G22 despite all my efforts and knowledge I'm quite far from competent with c++ to do most of the code merging/refactoring to bring the theming features across from RetroPie's fork of EmulationStation. (read: I'm not a programmer and enough has changed between the two code bases it's not just copy/paste work).
As for marking the end of Recalbox, I don't see how that would be such a thing? All the code is out in the open and they can do what ever they like in regards to porting features over.
nadenislamarre You may want to look at my reply just above about some discovery work I did around video thumbnails and other RetroPie features and my paragraph below about thoughts I have about how to get such a feature brought in...
My take on all this is if Batocera wants to bring RetroPie's theme and other UI enhancements in I'd suggest looking at forking RetroPie's ES codebase and add back the menu items Batocera currently has as well as looking to see if one could do away with using configgen and co-opt the RetroPie launch script. Finally I'd also be suggest where possible members comfortable with c++ actively try to maintain merging in upstream changes so feature creep between the two projects is minimal.
Again, the above paragraph requires agreement from all involved in Batocera so contributors efforts can be organised and the work gets done with out people losing interest.