Int probably won't be too high, yeah. I'd dump Str first though. Possibly Wis too.
Yeah, Concentration's the one skill they can't do without. Other than that though...
A couple ranks in Spellcraft don't hurt, as it's useful with their detect magic ability. Knowledge (arcana), too can be useful but they probably don't need to max it if they don't have many points.
UMD can be handy but not everyone will max it.