I actually do leg presses, curls, and extensions in the routine I'm currently on.

Program 4 here

But you're right. I might try eventually phasing squats out, or at least taking them a little more slowly in the future. Maybe replace them with Smith machine squats.

The box squats felt good yesterday, though. Having to sit up from a stool forced my hips to take most of the weight and kept my lower back straight. Usually I have the tendency to shift the weight onto my quads or even lift with my back if the weight is so heavy. Gonna try these for a while.