I mean, when I join a league, it gives me a team. So if I joined a league and then managed a commish team, would I have two teams or would doing what you described invite me in as a co-manager only?
While you would appear as a co-manager in the league where you are commisioner, you would not actually participate. You WOULD participate in the league where you are not commissioner.
I know it all sounds confusing.
Here's what you should do:
Just take these steps. Delete my team in your league. Invite me to co-manage your team. I will play your team. then make me co-commish in case you can't commish for any reason. I will run that team and be your backup.
Next, in the league you wish to play in, IF you want to play, ask that commish to delete your team and invite you to co-manage. Then they should make you co-commish. You will be their backup commish.
Did I explain that well or what is confusing?