One possibility might be if I can make RetroFab available on RetroArch, then it would work on lots of platforms, including the handheld consoles you mentioned. I'll need to investigate further when I have time.
Viewing post in Player for handhelds
Nice idea, it will be a pleasure to have its in Retroarch using a specific core to launch your .sim files. We are developing a retro gaming OS as Recalbox/Batocera called pixL-OS, I will be happy to have integrate it ;-) Keep me informed. Today I just did a version where I called url from internet but it's not usefull.