yup people have been suggesting this. There was a "great blitz" thread with like a hundred replies, if you want to search it and read some of the arguments.

As for CV, a mid ranged battle room will more than likely encourage you to keep running locals and bombers without the lessons that fighting Tier 4 fighters can teach you. Once you suddenly hit the high level battle room, similar to when players graduate from blitz, they will not know how to deal with high level CV or line battling BB who want vision. Playing mid level CV in the current GB, you can still be a helping member of your team and you can still kill some T4 with some skill.

As for BB, BB123 who is use to rushing would not know how to line battle or yet how to fight against a line battle if they suddenly join a BB456 room. The current GB teaches them patience and only rush when the enemy is blind, for example.

You know that they are bussy with greating Harbor Assualt for all players?
So they are working for new gameplays.

SDE doesnt want us to play anything other than GB.

everyone gose threw this ive went threw this 4 times with BB and 3 times with CV it will be a lil rough but everyone can do it takes some time and teachs you how to play if your new i find it fun sometimes to play with low lvl ships and crew just to get that newbie feeling