@temrix Since you are a developer, you can use the Recalbox source code to modify as you like as long as you respect the license, Recalbox is an opensource project:

A simple user cannot install anything, as it goes against the original idea of the Recalbox project, which is to be as ready-to-play as possible. Really Retropie is a system whose idea is that users install everything they want, the principle is practically the opposite of Recalbox (though obviously both are focused on retroemulation), and automatically to be this way, Retropie "forces" the user to install and configure everything from basic to advanced (and it's one of the reasons I prefer Recalbox).

Unfortunately, as I'm not a developer (I'm a "simple" user) I don't have enough technical knowledge to support you on how to build your own Recalbox build, and that's not the kind of support we give on the forum either, but the instructions are at the link above, in case you're interested.