Who says you need to win? You just need to ensure you don't get a 3rd game, which, in the OP's case, should be extremely easy to control, be it losing both or winning both. He clearly stated from the beginning that teams in his league can't demote.
I understand that. If losing a relegation series without demoting is equivalent to "demoting" and "bot promoting" then you'll have 2 effects conflicting: the demotion and the bot promotion (it's a fair assumption that if one is taken into account, also the other is). The end result is difficult to quantify, but I agree that you probably lose some revenues the following season. However since you can also build seats (if you're not capped) or generate profits with the extra revenues that should absorb some of the potential losses.
Both promoting league champions and teams that promoted from a bot cleanup will get the extra cash, though bot-promoted teams will not experience the same boost to their season ticket holders.