I'm a little biased since I've been playing the game for so long, but I think most of the fights (Beach included) are beatable upgradeless. I see your point about losing progress though.
If you're worried about that, I'd really recommend you do what I did and download one of the previous versions of the game.
Then:
-Cheat in the money
-Download the latest update
All save data is maintained between updates so far, so the cheated money will carry over as well as any scores/victories you get from now on. It's worth it imo! The game doesn't really take up much space.