This would go a long way toward fixing how broken the current system is. Leveling one class through nothing but dailies from 50-75 takes months with no daily resets. Not just a few, either. It's ridiculous how long it would take...and then you have a third class to worry about.
Wanting to use being able to level your secondary faster if you use the cash shop is one thing, but spending months on end leveling just one class, when you already need to keep doing dailies on your main class until it caps (which depending on how casual you are, could take a few months in and of itself), is beyond excessive. Even if it takes half the time or even a third of the time to level a second or third class to 70+, they'd still sell a lot of daily resets, because there's always people who either don't have enough time to do dailies every day or don't mind cutting corners by using money to bypass the amount of time it would take to level those classes without spending.
Something needs to be done, now that 60 elites are out, with 70 elites probably soon to follow. The current system simply does not work, and will dissuade a lot of new players when they find out how long it'll be to get their last two elites without dishing out a crapton of money. The game is pay-to-win enough with the gearing system alone.