I had thought this would work for quite a while, but I recently had the chance to try it out. Forgive me if this is a bit elementary, but I was off the game for a long time and only recently downloaded 0.33 and haven't gotten back up to speed on all the developments.
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When Govannon trains a unit it gains Channeling I and Sphere I of whatever he teaches.
This is a nice boost for arcane units, as they don't have to use a promotion gaining the sphere. For other units it gives them a nice trick ability and with Death mana it provides a ton of slots for summoning a horde of skeletons.
However, it seems to me that by far the best use for Govannon's tutoring are disciple units. A priest has Channeling II. With Channeling I they gain full access to the arcane spell progression for the spheres they are taught and since High Priests pick up Channeling III, they get archmage level spells as well. You may lose some of the special Amurite XP bonuses for mages, but it's still a wickedly powerful path.
In addition to the straight disciple progression many priests have upgrade progressions to non-disciple units, giving access to Arcane units without weakness to those annoying assassins.
So, just some few ideas off the top of my head. I'd love to hear anyone else's recommendations as well.
Amurite Druids
If you never choose a religion that changes your alignment (which is most of them) then Druids make for a good long-term goal for Amurites. You will need Archery for Firebows, which means you're also starting down the recon/nature path. Regardless of how you choose to get to Druids, adding up to 5 spheres by Govannon is obviously nifty.
However, if you upgrade a priest to a Druid, you have the religion and Channeling III and Divine, which gives your Druid the special abilities of a High Priest of the religion, e.g. a Stonewarden upgraded to a Druid gains the Earthquake ability of a Runekeeper.
Most importantly, this is very fast as you don't have to wait for a unit to level up as you do with all the other Tier 4 spellcasters. All it takes is the time for Govannon to cast all the training. Build a priest, then upgrade to a Druid and have Govannon train him. You now have a Druid with up to 6 spheres and all the special abilities of a High Priest and you have yet to spend the first promotion. You may even have picked up the XP for a promotion or two just in the short time it took to do the training. These Druids make Balseraph Harlequin-Druids look like magical chumps.
Disciple Liches
Since Govannon can train Death sphere and Summon Skeleton is incredibly useful (especially with huge numbers of Death I slots for skeletons), it's a very common strategy to chase Death mana. Once you have a High Priest or Druid trained by Govannon up to Death III you can have them cast Lichedom to turn them into a Liche. They will lose some innate strength. However, they retain their former powers and open up the limited National Unit slots for more promoted disciple units.
Combat "Magi"
In my experience, Mages die horribly once the enemy sends out assassins. While not hugely more powerful against such things, priests are nonetheless a more durable spell platform. More importantly, they can immediately start buying Sphere II spells which is nice when you are replacing casualties during war. Of course, Amurites can often effectively produce Mages right out off the gate as well but the disciples are still tougher. Train Priests to send them out with combat stacks. Leave the Magi at home to buff cities and units and age into the Archmage slots.
Trained Priests may also be upgraded to Paladins and Eidelons. While you might not want to waste a promotion slot for one of these combat units on a spell, it might be worth it to have magi that can actually beat back an assassin. Firebows can provide plenty of fireballs on the offense, but having a Paladin that can drop Regeneration and Shadowwalk on the stack (along with the level 1 Haste that many units will be able to cast) can allow you to blitzkrieg the enemy territory without needing to stop for healing or to bombard cities.
Archmages Everywhere
By the time you add up Archmages, Druids, High Priests and Liches, Amurites have a massive 16 slots for Channeling III arcane spells. Admittedly, 4 are limited to the Govannon spheres, 4 to Govannon spheres plus Nature, and the Liches might be limited, based on the path chosen. However, the paths to choose from are pretty good and any limitation in path comes with the auxiliary powers of Tier 4 disciple units.
I'm sure the response here will be "yeah, but by the time you've got all that, you should be winning anyway." Well, maybe so. It's still fun to consider.
And, again, I really think the strength of it is via the Druid path where if you have the gold to do it, Priest/Druid/Liche upgrades can fill 8 national unit slots extremely quickly when you end up facing a late-game enemy who is also throwing a huge army into the fray.
===
That's just my first think-through for the new edition and much of it is recycled from ideas from previous editions of FFH. However, with the changes to the magic system I thought it might be worth revisiting. I'd love to hear what others have come up with.
Also, one thing I'm not clear on is if Govannon can train allies' units. If so, that opens up a whole other set of strategies for vassals and such.
===
When Govannon trains a unit it gains Channeling I and Sphere I of whatever he teaches.
This is a nice boost for arcane units, as they don't have to use a promotion gaining the sphere. For other units it gives them a nice trick ability and with Death mana it provides a ton of slots for summoning a horde of skeletons.
However, it seems to me that by far the best use for Govannon's tutoring are disciple units. A priest has Channeling II. With Channeling I they gain full access to the arcane spell progression for the spheres they are taught and since High Priests pick up Channeling III, they get archmage level spells as well. You may lose some of the special Amurite XP bonuses for mages, but it's still a wickedly powerful path.
In addition to the straight disciple progression many priests have upgrade progressions to non-disciple units, giving access to Arcane units without weakness to those annoying assassins.
So, just some few ideas off the top of my head. I'd love to hear anyone else's recommendations as well.
Amurite Druids
If you never choose a religion that changes your alignment (which is most of them) then Druids make for a good long-term goal for Amurites. You will need Archery for Firebows, which means you're also starting down the recon/nature path. Regardless of how you choose to get to Druids, adding up to 5 spheres by Govannon is obviously nifty.
However, if you upgrade a priest to a Druid, you have the religion and Channeling III and Divine, which gives your Druid the special abilities of a High Priest of the religion, e.g. a Stonewarden upgraded to a Druid gains the Earthquake ability of a Runekeeper.
Most importantly, this is very fast as you don't have to wait for a unit to level up as you do with all the other Tier 4 spellcasters. All it takes is the time for Govannon to cast all the training. Build a priest, then upgrade to a Druid and have Govannon train him. You now have a Druid with up to 6 spheres and all the special abilities of a High Priest and you have yet to spend the first promotion. You may even have picked up the XP for a promotion or two just in the short time it took to do the training. These Druids make Balseraph Harlequin-Druids look like magical chumps.
Disciple Liches
Since Govannon can train Death sphere and Summon Skeleton is incredibly useful (especially with huge numbers of Death I slots for skeletons), it's a very common strategy to chase Death mana. Once you have a High Priest or Druid trained by Govannon up to Death III you can have them cast Lichedom to turn them into a Liche. They will lose some innate strength. However, they retain their former powers and open up the limited National Unit slots for more promoted disciple units.
Combat "Magi"
In my experience, Mages die horribly once the enemy sends out assassins. While not hugely more powerful against such things, priests are nonetheless a more durable spell platform. More importantly, they can immediately start buying Sphere II spells which is nice when you are replacing casualties during war. Of course, Amurites can often effectively produce Mages right out off the gate as well but the disciples are still tougher. Train Priests to send them out with combat stacks. Leave the Magi at home to buff cities and units and age into the Archmage slots.
Trained Priests may also be upgraded to Paladins and Eidelons. While you might not want to waste a promotion slot for one of these combat units on a spell, it might be worth it to have magi that can actually beat back an assassin. Firebows can provide plenty of fireballs on the offense, but having a Paladin that can drop Regeneration and Shadowwalk on the stack (along with the level 1 Haste that many units will be able to cast) can allow you to blitzkrieg the enemy territory without needing to stop for healing or to bombard cities.
Archmages Everywhere
By the time you add up Archmages, Druids, High Priests and Liches, Amurites have a massive 16 slots for Channeling III arcane spells. Admittedly, 4 are limited to the Govannon spheres, 4 to Govannon spheres plus Nature, and the Liches might be limited, based on the path chosen. However, the paths to choose from are pretty good and any limitation in path comes with the auxiliary powers of Tier 4 disciple units.
I'm sure the response here will be "yeah, but by the time you've got all that, you should be winning anyway." Well, maybe so. It's still fun to consider.
And, again, I really think the strength of it is via the Druid path where if you have the gold to do it, Priest/Druid/Liche upgrades can fill 8 national unit slots extremely quickly when you end up facing a late-game enemy who is also throwing a huge army into the fray.
===
That's just my first think-through for the new edition and much of it is recycled from ideas from previous editions of FFH. However, with the changes to the magic system I thought it might be worth revisiting. I'd love to hear what others have come up with.
Also, one thing I'm not clear on is if Govannon can train allies' units. If so, that opens up a whole other set of strategies for vassals and such.