As others have noted, you only need to be 80/80 to use the sword skills. That being said, your suggestion would require notably increasing mana generation and possibly adding skills that manipulate the gauges (a skill that removes mana from one bar and adds it to the other) for it to be considered feasible. You'd also have to change the rate at which mana is intended to be consumed (and likely nerf a bunch of abilities as a result). It would take a bit of work, to say the least.