I think the whole issue of mix'n match brake parts is greatly exaggerated.
Most riders will have ridden bikes with very different brake setups, or even the same bike with very different brake performance under various weather conditions w/o any critical effects.
Dry/wet for instance, or that nasty, but yet desired surge when a few turns have squeeged the rims dry can easily change brake characteristics just as much, if not more than mismatched levers/brakes.

Pretty much anything is rideable, as long as the rider knows the bike, and adapt his/hers behaviour according to the situation.