Is it possible to mod a hero to have random spells?

[OleSwifty]

Title says it all.

I like the idea or mystic X or warrax to have assigned random spells they know.

[I like Serena]

Title says it all.

I like the idea or mystic X or warrax to have assigned random spells they know.

Yes.
You can you the Real-time Game Tweaker to open MAGIC.EXE and edit any hero you want.
Each spell casting hero has a number of spell slots. In particular a spell slot can contain a random wizard, a random fighter, or a random 'any' spell.