Like I've mentiond earlier I made this thread because it would seem Cyanide wants to keep their inducement system. Having a more sophisticated bank rule sounds like compromise everyone could live with. I really like your concept for Spiraling Expenses, though. Would definitely fix some of the issues with high TV we're experiencing currently.
To get back to your suggestion, the bank as it stands is something of a risk vs reward thing. If you want to be able to save for that blowout then you take the hit in terms of TV, whereas if you're willing to take the risk then you stick rigidly below 150k (or whatever you set the bank to).
The system as it is now is way too punishing. I really don't get why we have this huge difference compared to other Blood Bowl platforms in BB2. If you really think there should be some kind of limitations to have that risk vs reward aspect I'd go with this:
Might work, but I would still count the playerpool money somewhat towards TV, not fully but some fraction. Reasoning behind it rather straight forward, money in the stadium fond doesn't involve and gain towards the game, while the other 2 pools can more or less directly influence the team/game.