Babbling a little bit because now I'm inspired. Feel super free to ignore.
I plan in making an angst so big that a fluff ending could never be truly achieved. I already enjoyed V3OC ending where she finds strength knowing she'll live for Momota, for both of them... but a widow ending, while really nice, doesn't offer much if I don't know what happened to the V3 cast...
SDR2OC, however, I can play with the scenario as much as I want since I know the ending.
Did you know the amount of bacteria in the human hand and mouth? I already headcanon that Gundham likes to scratch and bite the legs of his beloved while going down on her. In Ultimate Despair, however, he does it with so much strength that it's impossible to not cut through the skin, leaving it infected since... well, bacteria.
Of course Ultimate Despair SDR2OC would love to watch her legs completely rotting away in the process, her beloved did that and that would bring her despair anyway. Future Foundation, howeve, was worried for her health since she could die... they had to amputate her legs before putting her in the Neo World Program.
After the events of SDR2 and DR3, I like to imagine that OC is in a wheelchair for the rest of her life, and she is fine with the consequences of it, Gundham however feels guilty specially since he is the one that caused this (even though she gave consent and was totally on board). No matter how much she smiles, calls his name, reassures him that she is fine and none of this was his fault, he'll never be able to forgive himself 100%. He makes up to it by doing his best to her everyday.