is it at all possible to give magic casters that have atleast half the type of mana a spell uses to get a bonus (lower mana needed to hold) for the spell?

I don't want the req to drop down all the way to similar magic with similar magic, as with bards and elemental, or paladin with a holy scroll and what not, but I do want it less then what it is now. Maybe somewhere between the two?

It just doesn't make sense to me that someone who doesn't have a clue about either mana types in the spell have the same ease holding the scroll as someone who understands most or part of the spells mana