I have to agree that I think the Wu Jen having a lot of unique spells is what makes them interesting. I've just introduced one as an NPC in my campaign, and the use of various Wu Jen only spells has really added some flavor. Without that, the various other little class features don't do much, and there isn't much different other than the name. Heck, in my campaign I've set Wu Jen and Warlocks up as opposing Orders (under different campaign-specific class names). They come from a land foreign to the PC's and are the only spellcasting available in that area. It's fun.
That said, if you aren't using Wu Jen, then I'd probably just throw all the spells on the Sor/Wiz list. No harm, no foul.
AD