I think it'd be neat to be able to bank certain spells and trade them between characters on your account. Obviously none of the base school ones/late game spells, but the 'special' spells, such as the crafted or dropped ones. I say this mostly because I know there's quite a few people who farm Loremaster + Packs for spells and end up with other spells that are basically useless to them (and I'm one of them. I have L. Weaver, Rat Spin, and Hammer of Thor all on my Myth. ) It'd be nice to be able to actually give these spells some love on a character that'd use them.
While we'd all love this to come to the game, the KI team was pretty clear in one of their recent streams that's they don't plan to add this anytime soon.
Easiest workaround is to make an F2P account to take your cards then switch wizards and trade back. Slower, but just as effective.