Well, it is possible to simply use the cartridge as a storage device, running from RAM and just loading from the cart as if it were a fast disk (even slightly easier, since there's no need for a DSR, it's just a memory to memory copy).
I did Mr Chin as disk for similar reasons, but I realized after the fact I could have just done a 'copy cart' and people would still have been happy. It felt like cheating at the time.
Right, but that still means completely reworking my game to have a different approach to getting data... Which means paging memory in and out for specific uses. It also means I have to be more deliberate about data being static; right now I freely alter static data in memory if need be, since I can... It's really a different style of organizing your program.