If an opponent would win the game, instead you win the game.
If an opponent would lose the game, instead you lose the game.
Basically yes. But I think the "not due to platinum mirror" has to be there, otherwise if someone would win then the other person would win instead. And then that person would win, so it would have to switch again.
Wait a minute, can't I just concede and cause you to lose when this is out?!
Im not positive but I do not believe so. I think concession will not affect anything in play. Otherwise you would not be able to scoop if you had Platinum Angel out. I could be wrong in that logic though.
Finally the "not due to Platinum Mirror" thing doesn't make sense. If I cast March of Machines and attack and kill you with it, is that "due" to the mirror or not?
Literally yes, how I invisioned it functioning no. I was trying to come up with a way to stop it from going into an infanite contradiction of itself whenever someone won or lost. I can't think of the wording I would need in order to do that.
I figured needing the 6 mana plus the restricted cards would be enough to keep the rougness in check, I could however be wrong, now that I think about it a bit more. Perhaps a higher cost? Or maybe this card is just to messed up to ever see fake print. I will try to brainstorm ways to make it less broken, other than just upping the cost. Although I don't know that there are any.