Something else (that I've proposed before) would be to attempt to ensure that new managers experience as much success as possible early on.
Currently, new managers are put into the highest possible league with openings (ostensibly to eliminate bot owners in these higher leagues). This makes success early on (something I believe to be crucial to retain owners) difficult - if you end up in that situation. Reversing this - having new managers start in the lowest available league for that nation - would give the owners early successes (even if it comes against bots), and that would help retention of new managers. Additionally, it's a more forgiving environment for them to learn, and develop their managerial chops before heading to tougher competition.
Just a thought...
http://with-malice.com/ - The half-crazed ramblings of a Lakers fanatic in Japan