Do you ever just tie them together?
I have 2 120ft ropes and a shorter one. Sometimes the 120 is too short. For access via footlock I just put a biner tween the splices so I have a 240ft rope When I get in the tree, seperate the lines and use a traditional system.
I have only done this twice. Yes it means you have a LONG footlock and you can't hit the ground once in work mode. To decend, I decend, stop, redirect the rope around the stem with my RG, and then hit the ground.
Note orange and green line together