Yeah, this one scares me.
Could OP perhaps edit a LOLB or ROLB to be a MLB for 1 game to force the sim? Then edit him back?
Then sign a scrub MLB and force trade it to the CPU team the following week before playing a game? (since you cant trade mid-week where his franchise is currently stuck.)
In any case, someone should post this in the bug thread, this could be a huge issue.