Push Press?

It's not a bad option.  I'm not sure that it's going to tax your legs any less though.  I would just go plyo exercises or maybe do high volume light pause squats.

My experience is that it's difficult to make generalizations as to how your legs will respond to a fairly high volume of endurance training and weight training. I've known people who could run and squat with little difficulty and some who have struggled. Here are some general thoughts on the matter:

* If you were stuck on an island with just a barbell, the power clean and push press would be an excellent choice pf exercises. It'll work darn near every muscle in the body very efficiently. And yes, I would add the power clean in addition to the push press. It will tax the legs somewhat but not as bad as squats.

* Plyometrics are great for legs and they carryover to endurance sports. Ease into them slowly because they can still be plenty taxing, and the jumping around will put a pounding on your joints.

* Recovery ability can be trained up to a point. Although you probably couldn't do both high volume leg workouts and train for an Ironman, you could do some maintenance work for legs while training for a HIM, for example.

* Related to the point above, you need to become your own coach. You may be one of the lucky few who can gain 50 lbs. on your squat while training for a marathon. Or you may need to back way off. The best way to do this is to gradually add exercises to your program each week and see what you can tolerate.

* Also related to the two points above, this is why I no longer like "programs." Sure, I can give you a nice weight training program over several weeks, but I don't know your body like you know your body and you may be burnt to a crisp after one week. Instead I go for guidelines or templates. A guideline for working the power clean + push press combo would be this: do 3-5 sets of 3-5 reps. First workout, just do 3 sets of 5 with a comfortable weight. Second workout of the week, push it to 4 sets, try to do a fifth set of 3 reps if you can. Do only 2 workouts the first week. Second week, try for three workouts. If you're feeling tired, stick to just two and wait until week three to get in three workouts. Week four, add weight. See how this works? It's a gradual progression. Each week we're adding something to the workout, and we're monitoring how you feel. If you can do more, great. If not, back off. Sets and reps are given as a range as opposed to "you must do 5x5."

Great post!  Thanks for the well thought out response.