Hey there, this mod does exactly what you think it does, it allows you to use multiple custom tilesets at once.
I don't plan on going anywhere with this, it's just a quick thing I did to, well, prove the concept. But if you have any suggestions, feel free to share them!
Also, I haven't added this to my own mod, but I'll do it if enough people want me to.
Includes the three edited files to add to your mari0_se folder, and a .love that runs the mod without doing that.
How to use: Make a "tiles" folder in your mappack, and place your tilesets there.