it is not really related to previous posts :
I see many references to AoW or DnD...etc
Do not forget that FFH added creativity, the system was (almost) ingenious and different from already exisiting magic systems.
It's fun.
If you take too many inspiration from other games, you may lose the originality of FFH and maybe have only a "lower quality AoW" as you implement mechanisms form a game into another one.
So, while, changing from the actual 4techs into 3 schools is ok, changing the way spells and summons work is also ok, but please be careful.
ok, on the subject at hand :
-could you explain what you really mean by "summons are rituals" ? does it mean the can only be summoned in cities, with

?
-How will domain spell work ? a mage launch the spell in a city, and "hop" there are "inspiration" buildings in all cities ? will it disappear if the caster moves ? dies ? launch another spell ?
maybe the cost/turn should rise with the number of cities? but what if you don't want to spend so much mana ? as you may have many cities, any "domain" spell may become too expensive to maintain, and you really want it only on some pinpointed cities...
maybe it works only for cities in the same continent ?
It will be hard to balance the + side of having domain-wide spells
-buffs/debuffs : I suppose if auto-cast (enchant blade), every newly created unit will get an enchanted weapon if the spell is activated, with a cost for automating the spell. But, what if you would rather have not used any of auto-activated spell, and just this time you would rather have launched 2 big costly damage spell /summon ?
..Etc