My notes on the modding system

I'm trying to make my own mod (The donut mod just wasn't cutting it for me) including all kinds of new content! The only problem is, I'm not one to lose content, or change it, instead, I add content to extend the game. I've decompiled the Lamborgotti mod and Classic Cars mod in order to get the files I need, successfully adding the Lamborgotti and the Teal Ferrini to level 1. Then, of course, the downside. As soon as I added a third car, (The Alien Cop Car from the Classic Cars) the game would not allow three purchasable costumes! With the introduction of a third car, the robed homer costume is just gone, not available whatsoever. I was hoping to add more costumes in the future as well, but there seems to be a maximum! Is there any way to include a large number of cars and costumes all in one level?

Not at the moment, that's an extremely difficult change to make.