NOTE: I, of course, don't know if any of these things might be in the game already.

Immortality Potion/Item - So your heroes/children (Or a couple of them anyway if you get lucky) can stay alive for ever, unless ripped apart by a bear or something.

Same as above, but a spell to make them come back as undead/litch (As posted before), possibly with some drawbacks, and certanily with some fire dmg mods.

Leather armor that's not made of animal..for those choosey evil necromancers (And their armies).

Incest: I have to say I wasn't really into this (heh) but the PAX videos recently put up about breeding the best heroes made me want this muchly.  Heh. 

Schools: Places for new children/heroes to go to refine their powers a bit before they go out to fight and die (Gives exp per turn but only up to a certain point, high upkeep).

Gigantism spell:  So you (Or better yet your chosen discipels (cant spell)) are on an equal (more so) footing with some monsters- can be for ever or just in battle map (aka two different power level/timing spells).

Chamelon spell: Makes one of your units LOOK like that of another race/empire - useful for inciting wars (aka Border Incidents) against enemies or sneaking up close - the coding with the AI being able to figure this out might make this only applicable for human multiplayer.

-----

Had a lot more but they would probably be much harder to add.

Feel free to add in with good ideas, or bad ones so mine look better.