The issue I am finding with my consideration is this. Even with the elastic gripper on the edge of my cycling shorts, that leg always pulls up above my liner and socks. I find myself riding along pulling at my shorts to get them to come down for a moment. I am afraid that just cutting off one leg is going to result in more of the same of that. At the same time, it is a real pita to try and deal with any leg issues, dry my liner, etc while wearing them full length. I am thinking of either dealing with the "pull down" or doing some manner of tuck like on the commercial I have seen with the Olympic runner.
I would suggest sewing something inside that area of the tights to protect them. From what you describe, I think the damage is being done from the inside - if I understand this correctly.
My bike shorts stay down on the prosthetic side when I wear them outside the suspension sleeve. I do often roll the sleeve up outside the shorts in warm weather, because it seems like a good idea to have that wicking material next to my skin. It feels cooler to me.
I tend to wear 1 or 2 layers of leg warmer on the non-prosthetic side. I do have some wind pants for really cold weather, and I use velcro or rubber band to make sure the excess leg fabric is bunched up away from the bike frame. I do have 1 pair of capris. I had a seamstress install a zipper in the leg on the prosthetic side, so that I could pull the capri leg up to do adjustments and sweat management.