The only imbuement skills that are worth using on spells are Guided Weapon/Homing Weapon/Shockwave/Shattershot IMHO. Multishot has potential too, but I feel that Guided/Homing of more important.

As for not requiring the advantage, I feel that Imbuement Skills are balanced by the huge UB cost of the imbue advantage, so leaving it out will cause issues. Even in 250+ point range it isn't trivial.