You also get forced into the thief solutions for the Rite of Peace/helping Gnome Ann, and the Black Bird, as well. Miss out on the Paladin solution IIRC.

As a wizard, you'll miss out on the thermonuclear blast spell (and an alternate ending, extra death), as Famous Adventurer will give you thief item instead.

As mentioned only wizards get access to summon staff quest lines, these are intentionally scripted into the storylines (since other characters get completely different storyline or puzzles in place of the need for the staff).