4 teams is less than 20%. I'd go with 6 teams or more for now. This way you end up with 20 teams with 1-2 unmanaged, which isn't bad.

RT should be just like Trad in the chance to have a redraft for their league.

As a bonus for anyone that takes over a team allow those owners the first chance to get into the new leagues being drafted.

Most importantly is to get launch leagues going again. I have a number of guys that would try a launch league.