A feature that would be very much loved is if casting a spell on certain objects would produce different results depending upon the spell and the object.

Example:

A custom spell called: "Enchant". (Purely example) on a sword, would make a "Floating sword" ally for the player. But if "Enchant" is used on an ID that is for say a bow, longbow, or even a stone if it'd ID was there, to become a 'Floating bow'. ally for the player.

Or a circumstantial "Summon" spell, that would summon a different creature based on what it is cast upon.

Imp Dust -> Imp

Wisp Dust -> Wisp

Unicorn Horn -> Nightmare

Tree -> Ent

Stone -> Golem

The "Reanimate" spell would also be much more interesting if it were circumstantial, generating a different type of undead based on the corpse used.

If that existed it'd certainly be possible via modding to do that then. Even if it wasn't in the base game, the capacity to do something like this through Mods would be a very happily seen feature :D

It's doable, I added that to the list. It requires quite a bit of rework for the ability system, so probably not sooner than v0.4