Well you COULD use the old levers. But I'm wondering why you want to switch? If the levers are not working well why not fix them? If you don't like the feel of how the brifters work then you'll still be stuck with them instead of the much more sleek and ergonomic simple aero brake levers. And if it's just that you don't like the feel of the Mirage brifters then selling them will put a bunch of money back in your pocket even after you buy the far cheaper aero levers.

If you really insist on this then I'd want to get proper indexing 9 speed shifting for the rear and go friction on the front. I love being able to trim the front to avoid cage clicking in the more useable but extreme combos.