[Sombre]

So far magic item modding is very limited - just what you see in the modding manual.

You can make new spells and put the old ones out of the way by giving them impossible path requirements (like Holy 6), yes. So you can have all the spells in the game be your own.

You can't change the name of the spell schools, although you could head each of them up with a level 0 spell which had a name like EVOCATION or whatever all in caps and would make it clear what the school was at the top of the screen.