The idea of multiple ladders for better MM experience was also discussed in this thread. The discussions are pretty much related, since it will fix both issues.
I do support the idea of having some different ladderes. We can even have some global ladder:
RM 1v1 → Just like now, this is the global ladder. This reflects your overal skill level and needs to be the most important ladder. I would say that the number 1 of this ladder is the true best 1v1 player.
RM 1v1 Open maps → Only for open maps, will be used in MM if you are playing a open map
RM 1v1 Closed maps → Only for open maps, will be used in MM if you are playing a closed map
RM 1v1 Hybrid maps → This will be used for other maps, like pure hybrid maps, but also thinks like water maps, Nomad, MegaRandom, MM will use this rating for this kind of matches.
After the match you get an update to RM 1v1 rating and to RM 1v1 rating. With this we can easily expand the curret MM system to even other kind of maps / game modes. In the end, most games are played on MM system, so we dont need any ranked lobby any more. If you go to lobby, most players will have accurate Elo from MM which can be used for teams in Lobby.
To me such system would look like the system of SC II which have proved itself if i much believe you. Just one note: This only works if the player base is big enough.
I am not a fan of ranked games against AI. But that is just me. It can be part of a completely different rating with no connection to the other ladders.