Right now the plan is to get feature parity, so I can move on refactoring the original code. For development, I have an XP virtual machine with the original dev environment for testing/comparing and developing on Linux with QT Creator. So I am porting to modern C++, integrating with QT, adding new features (slowly). The original program was developed with Microsoft Developer studio around 2008 with stuff of VC98, written in C/C++.
The original thread where I am leaving updates: Repo: It is a tool that add a trainer before the original rom start and support some cheat system like codebreaker or raw. I started since few days on working on the original source code of GBAATM, that I got privately from the original author with permission to work on that.