I like that idea.. as i matter of fact i think with your second idea that plan makes more sense.. but instead of the top 3 take all playoff teams and the bottom 12 from each and expand it from 5 to 50.. thats 1600 players.. idk if thats an accurate number for how many that play this but that would truly give beginners like myself an idea of how good they truly are.. if you cant beat a computer based league that you may or may not be placed in then you need to get back to the drawing board.. the higer you go you the less computer based teams you would compete against. You would naturally fill slots from player with most wins to least, and the rest leave open for future players to join so they wont necessarily have to start in league 50 unles they really wanted to. And once you reach that 50th league being halfway full with human players then open a new league.
Only other change with this new set up would be to allow the first change of the team name be free and if you decide to leave for whatever reason you may have the next player to takeover would pay for name change.