This is not Season End related, but should be answered anyways:
Do you intend to change pre-game lobby in any way or form? Afterall, it currently displays the most amount of negativity. People not getting the "role" they want to play seems to be the main cause.
You have properly discussed the issue alot internally. You do not want to force some kind of meta - a good decision. However, don't you agree some kind of change is needed?
A team where everyone gets what they desire to play, at least, rolewise - that would be a great change.
If you can't talk about it, I do understand.