Hey there, I'm glad you liked it!
That's a really interesting topic, but I don't understand much of the information on that page. It seems to require hardware modification to the cartridge circuit board that goes beyond the addition of the battery wiring, so it wouldn't be as simple as replacing the ROM. Alternatives for accessibility are always welcome though, so that'd be good.
To answer your question, yes, the hack was all made on the original mapper and the conversion was done only because of the save feature, so it is probably possible to revert it and follow through with the instructions on those pages to get the hack to work with battery save on a modification of the original board. I'm super focused on the production of my next game now, so I can't go back to hack work for the moment. I may revisit this game in the future, and that'd be a perfect time to take a look at this, among other things. I guess if an experienced hacker wanted to do it himself I could help with some guidance.