Minato would mark the ten tail demon (minato mark the tentacle of killer bee, that mark moved to killer bee), that mark would move to edo madara. Then he would go save shikaku and ino's father. and redirect ten tail demon back to the ten tail demon (minato redirected the nine tail demon fox's bomb to a safe place with teleportation barrier which means he controls where he wants to redirect) at the same time teleport next to madara and seal him away (since he knows a lot of seals, his specialty is seal) and hit obito with rasengan. Edo madara won't see it coming since what I have just said here, would happen in a matter of seconds. Ten tail demon will be without the mind of obito and edo madara and will go wild. Minato wanted to put a barrier to stop the nine tail demon fox before kushina put hers. My guess is that within the vast knowledge of seals that minato has, he would have a seal strong enough to seal the ten tail demon at least for few days. He knew a seal as strong as 8 diagram seal and since uzumaki clan were specialist on sealing monsters then kushina would have taught some to him. Specially since kushina herself was the nine tail demon fox. If by accident the nine tail demon fox got out, kushina taught minato a way to stop it and seal it again.
