Here's the problem,
@Darksoft or
@Mitsurugi-w or
@Apocalypse can probably confirm if I'm wrong on any of this.
It's not as simple as writing a menu to select a game because the LCD screen is attached to an Arduino which is in turn operating an FPGA (multiple FPGAs?) on the multi board
In order to have your on screen menu you have to write an interface for the 68k on the CPS1 or CPS2 to talk to that FPGA and give it the same instructions that the Arduino does.
You have to fit that menu and those instructions into a small enough space that the game you want to load can still address and use all the memory space it requires since if your menu is in any of that space, it'll crash.
Given how much code is going to be required just to interface with the FPGA ignoring the code to actually have the menu itself and the code to all the FPGA to load each of your 30+ games - your chances of fitting it into the quite possibly zero memory space left when loading the largest game on the system (Hyper SF2 Anniversary)
The MVS was designed from the ground up to have a menu and the Chinese bootleg carts had already done it, so there was a blueprint in place for a menu system and proof the memory space existed to make it work.
The Chinese bootleg CPS1 and CPS2 boards used an external screen. I just don't think it would be possible to have an OSD without adding additional memory to the multi B board and booting that first, then booting from the flash ROMs once they're loaded.
It would be an enormous task and a significant increase in price both in design and testing and manufacturing cost to make it happen
