Switching PBEM-opponent to AI

[Imp]

Finding a human opponent replacement will be the best solution IF you can get his game password

If its a secure game so requires a password the game is dead as it has to be played on the same computers it was started on.

If it is an unsecure game however another player could indeed take over if they wished.

[Roman]

if you set basic security you can use the pass of your opponent. but you should request the pass to your opponent.