There is a secret homebrew mode in the MRUpdater that lets you flash any gb/gbc rom to your Chromatic carts. I've seen posts that mention it as a possibility but no instructions or links. I imagine it wasn't included in the MRUpdater to prevent piracy or maybe its intended to be released in the future. You just need to patch the official MRUpdater.exe from ModRetro to unlock it. Its a fun thing to do and I kinda like swapping carts but using expensive game carts that only hold one game is a little silly when flash carts like Everdrive exist. but for anyone interested, links are below.
You must install python first then just download and run the patch_mrupdater.py
Navigate to your MRUpdater.exe and click patch.
https://github.com/Scryptkeeper2006/Modretro-Homebrew-Unlocker