aside from having to abide by the augmented limit, there's no restrictions put on attribute bonuses.
That being said, the question of physical spells and astral projection is a thorny one. One one hand, the spell only has to modify your brain, because your brain generates the mind/aura. On the other hand, the aura can't be touched by physical spells after it leaves the body and therefore it can't benefit from increase attribute.
There's no official clarification on this. (nor was there for 5e, so the uncertainty is nothing new for this edition...)