Honestly I don't think that's a good idea. Axers already dominate mages, and other dexxers are on par, and for mages it would just prolong the fight (maybe even to the point where both mages just run out of mana and need to withdraw).
It might be a nice idea for PvM, however the Defense tali already pretty much makes you invulnerable in PvM.
I do wish gems had more of a purpose in the game. I remember they used to charge comm crystals, but we don't have those. Mostly because of tech advancement in real life (IM's, skype, ect-ect) but I still kinda wish we had them.