I don't see a problem mixing the brakes and if you mixed pad formulas you could minimize the lock up risk. Their breaks, for crying out loud, like cars which have disks on the front and drums on the rear, it is all about setting them up so that the rear doesn't pull as hard as the front. That can even be dun by adjusting the cable length so that the rears have less pull than the fronts. (Speeling intendenal, in spirit of thread.)
Definitely go with the suggesting of the mix n match Tektros to get the different pulls.