I still have much things to study. I can successfully access to the shop, but i haven't tryed to install more themese at once. I actually didn't edit the icon for now. It just edit body_LZ.bin.
This means we can use existing themes as base to edit, and create our ones. Support for more, or fro creating from scratch will be implemented later.
As for creating CIAs, i rebuilded the latest makerom GitHub, and used it to do the work. I'll share my batch scripts later.

Well, not much, but at least something good.