Barring new champions from ranked

I know this issue has been talked about, but I have an idea that may or may not have been discussed: Disabling new champions for the next week or so in what I like to call Decisive Games. Decisive Games are matches that include at least one player that is currently in their promotion series or is on the brink of being demoted. This would, of course, call for some sort of indicator in the lobby, but it wouldn't show who specifically was in their promos or was about to get demoted. Just and idea, I haven't really given it much thought, so any criticism is more than welcome.

I would also like to say that, for no other reason than to be able to see the results of the pole, I have voted "Good Idea". This does not in any way reflect my real opinion, as I have not given this issue enough thought.