Why not some original Bill Starr 5x5? It's simple, fairly short, and should work fine for anyone in the ~intermediate range of strength...
Heavy, Light, Medium.
5x5 Back Squat
Heavy Day: ramp up weight to a top set of 5, making 5-10 pound jumps each set
(ie. 90, 95, 100, 105, 110), each week add 5 lbs.
Light Day: Ramp up the first 2 sets, then three sets across.. same weights as your heavy day (90, 95, 100, 100, 100).
Medium Day: Ramp up 3 sets, then two across.
Specificity + Frequency = win?