Since your upper body is your strong area, why not combine some of your upper body days like this for example, chest & triceps, shoulders, back & biceps, rear delts, and do a training cycle for 8-12 weeks of lower body twice a week.
It could look like this:
chest, triceps, shoulders
lowerbody with emphasis on quads, rest
back, bicep, rear delt
lowerbody with emphasis on hamstrings
rest
rest
You could do aerobics on your rest days and/or on upper body days after wt training. Abs,fit in when you like. Calves on lower body day.
Include some single leg training, such as single leg squats, single leg deadlifts and single leg presses.