They will finally make their return in 2 weeks time (especially glad about the druid making its return myself... And the bard looks neat as well so far.).
I agree that it was truly lacking in that part so far.
But can basically understand why they did exclude those classes from a design perspective (time for testing the mechanics which make the new core and covering different aspects of the game in different books each (while churning out books like crazy. No more comprehensive things mostly. DMG excluded.).
4th is much more of a tabletop than 3rd has been. RP is even more dependent on the GM as has been in 3rd (basically everything RP-Related is now in the hands of the GM with few rules on the matter.).
They probably speculated that the old fans would come aboard anyways later on (when the more story-based classes and races come along. If that will hit the mark will be seen...) and thus focused on acquiring new players first (while conveniently harvesting those players who migrate despite the lacking classes / races.
). Hence the selection of races in PHB1 as well which i have also not been very fond of... In spite of that all i migrated to 4th and have had quite some opportunity to play. All in all I'm glad i did. The even much stronger focus on Teamwork is what i like most..
I wouldn't be very surprised if PHB2 would be much more about the RP part of the game. Since the combat + character creation part is mostly covered in PHB 1. And i doubt that the PHB 2 will be much thinner than PHB1.
If that's true for content as well will have to be juged when it comes out....
I would recommend you wait at least until PHB 2 comes out in mid-march (to have at least some sensible selection of classes to cover all the basic lines. The classes after all are much! more narrow then in 3rd.
As is multiclassing (which is very hard to do compared to a 3rd Edition sense. The multiclass feats are mostly a side-note now... That in fact might be a boon in what you try to do here since mixing and matching the paths in FFH2 while possible is rather hard.).
I guess about 25-30 will be needed to cover the full scope of the 11? classes of base 3rd Edition. Thats inherent in the new system. Expect many more Players Handbooks to fill the various mechanics covered in 3rd.), use the classes which fit to a concept mechanically! and then strongly re-flavor those classes to match the lore.
No need to stick to wizards as arcanes (or especially clerics as divines which by no way will cover the divine line of FFH") just because they are called that way in the PHB and trying to reinvent the wheel. When you just need to go shopping for the fitting mechanics and slap the fitting lore (which already exists in the mod galore.) on top.
The other way is bond to be pain and by no means guaranteed sucess.
I for one would suggest you go with the cleric class for the arcane line and use a reflavored "channel divinity" feats for the spheres (3 per sphere. Fits with 1 cast per turn as well with channel divinity being an encounter power.
(because wizards are much more crippling / battlefield control-oriented in 4th. Invokers from PHB 2 might fit here as well... One of the primal classes (don't know for sure if its the druid or the shaman) encompasses summoning. So that might be a good fit here as well.)
The only problem here would be healing which should be the domain of the divine line. But thats not as hard to slap on the "wizard class" / other controllers as trying to get the rest right... (balancing it well would still take some work but i guess that could be compensated by adding a bit of versatility via some utility things here because the cleric is a rather narrow class by itself focused on healing and channel divinity as well as some ranged and some melee powers.)
The Warlock and to a lesser extent the Wizard might be a good base for the very diverse divine line (with the Paladin for the more combat-oriented part of the divines like Crusader, Stygean Guard or Paramander and the things following it). (and of course possibly Shaman and Druid in PHB2. Perhaps the Sorceror whould fit in here as well for some religions...)
Just make each of the 7 main religions a different class. Or at least the more strongly difering religions (or possibly do so with different paragorn-paths.).
For the recon-line Rouges of course still fit. (Wardens + Avengers from PHB 2 might fit here as well.)
For mounted line the Ranger oddly might be fitting (combination of skirmishing tactics, solid ranged + melee possibilities.). The Ranger is much less wilderness oriented now (thats the domain of the primal classes now mostly) than the class has been in 3rd (some other classes might fit in here as well).
While retaining enough features to still have the necessary skills light cavalry needs to process. (heavy cavalry like chariots and knights on the other hand might better be covered by other classes.)
(The barbarian might be a good fit here to. Remains to be seen.)
Here the problem might be that the ranger would also be a the most obvious good fit for the archery line (warlock or sorcerer might fit as well if strongly re-flavored.).
For line Melee fighter of course is a good fit (as might be the Barbarian from PHB 2.)
The warlord class might fit into different lines (as might the Bard from PHB 2.) and might fill what lines are not covered to your liking if the mechanics are to what you envision for the line.
Siege would have to be covered by equipment since no class i can think of could sensibly emulate that.. (But large-battlefield things are high-paragorn or low epic tier + now anyways where the high-tier units can deliver simmilar results anyways.)
For Races its similar. Better stick to fitting mechanics and then slap the flavor on top (Elves still likely fit for elves.
But Eladrin for example might be better fit mechanically for the amurites for example.
Humans wouldn't really fit all the human civs in FFH2.
But still need to cover multiple ones since the selection isn't 21 even with the PHB2).
What plays very much into your hands is that the new tiered system of D&D 4th coincides quite nicely with the tiers of FFH2.
Heroic tier can be conveniently used to depict Units of Tier 2 Melee (Axemen), Recon(Hunters), Mounted (Horsemen/Chariots) and Archery (Archers) as well as Tier 1 of Divine (desciples) or Arcane lines (adepts.).
Since Heroic Tier in 4th already skips the very start of the career with even the Level 1 Chars already being formidable combatants you should just skip Tier 1 (Warriors and Scouts) outright.
With the Paragorn tier used to depict Tier 3 Melee (Champions), Recon (Rangers and Assasins), Mounted (Horse Archers and the likes, perhaps Rathas or metal Chariots) and Archery (Longbowmen, Nightwatches) as well as Tier 2 of the divine (various Priests) and Arcane (Mages) lines.
But be cautious! not to try to solve all! the different spheres / faiths just by differing them via paragorn path (which even can provide slightly more than that anyways.).
Since the base class and the at-wills are the most influential choice for a character in 4th (paragorn multiclassing which is real multiclassing in the old sense conveniently ignored here.
), effecting the character trough his whole career with about equal (albeit quite a margin lesser than the class choice) importance of paragorn / epic choices.
If you try for example to differentiate Confessors and Ritualists via a Paragorn-Path that is bond to fail mechanically.
1 class may! encompass 2 or at best 3 different faiths of FFH2 (the mechanically and morally close ones mostly...).
And epic tier might conveniently depict the various Tier 4 Units (Archmages, Druids / Paladins/..., Phalanx and Immortals.). I think the biggest deal will be to get the classes and paragon-paths right
Provided you want to go with 4th at all since it really is a different game mostly (with the same core D20 system but the rest is changed so it becomes a different game.). I have my doubts if 4th in its current condition
(new, not fully fleshed out. Narrow selection possibly even with the Phb 2 tossed into the mix) can do the World of FFH2 justice (perhaps in a year or 2 with another set or 3 of additional classes.
But that doesn't mean of course it wouldn't make sense to get the basics right and expand later when additional classes come into the mix.).