You underestimate the gap. I thing above 1600 the gap is pretty small, how lower the level, how bigger the gap. 3-5 is clearly not enough at lower levels. Note that at lower levels players wont always play that frequently. 3 games can probably take a week or even more. It is not like you play 3 games every day. 10-20 games to get fair games is really no bad estimate at that level.
With the current system players are learning the game more allround. That makes this less of an issue. Ofcourse it also happens now too. The issue will grow if we add unlimited bans. It is most likely a issue if you go from closed maps to open maps (not the other way around). And i think it will be also more an issue for team games than for 1v1, since BF is much more played in team games than in 1v1.
Currently there seems to be some issues with team game rating. Yes, i know this idea is focused on 1v1, but if you give unlimited bans to 1v1, i think you have to do it also for team games. I think for team games the request is more like they wanna play Arabia or BF mostly, depending on the person. So i do understand why @MythicBubble289 is talking about team games too.
So in the end, i think having more ladders and maybe just 1 overalll ladder for RM 1v1 and RM team games will have my preference. This whole idea came up in one of the threads (i dont know if it was this one), where some other guy even said that in SC2 there is a rating for EVERY duo/trio. So for 2v2 games you have just a general 2v2 rating and a 2v2 rating if you team up with player A and a 2v2 rating if you team up with player B, … That shows us how specific the ratings can be. He also said SC2 matches are always great, which i will believe. (note i dont say we also need that many ratings for this game, it is just an example of how multiple ratings work).
I think MM can be improved by multiple other ways too. I dont think this is the place to share all my ideas. Maybe i will my own thread to just share all my thoughts, because it will be really offtopic.
More freedom is better and will win. I can tell you that too without a pool. In the end my vote will go to 3, but with the side note they need to have a look at the Elo, so match making will still generate good games.
Again: I am not against more influence for players who play against their map. For me the question is not ‘Do we want more freedom over the maps we play in ranked?’ but ‘How do we improve the match making system and give players more freedom over the maps we play in ranked?’