That's not actually addressing either of the points I was trying to make with that post. Apologies, I shall be clearer:They're on a island with Forge, Dr Nemesis, Beast, and Mr. Sinister.
They have the technology. And considering that superpowers can come in shots and inhaler form with MGH and Kick, those four coming up with a solution that's permanent via aerosol inhalation wouldn't be invasive, traumatic, or outside of the realm of possibility.
Making guinea pigs out of M-Day victims in order to perfect their super power prosthesis is likely to be traumatic.
Prosthetic, no matter how effective or lifelike, are not a surefire fix for the damage caused by traumatic loss of a piece of yourself.
If the goal was simply to have combat ready mutants, sure, your idea works. But if the goal is to undo as much of the damage of M-Day as possible? Not so much. Especially since it's trying to find a fix for a problem that already has one not because that fix would be more effective, but because you find it less distasteful.