I’ve actually picked this project back up after putting it on hold for several months. I have a PCB design completed which supports up to 128Mbit ROM and 128Mbit expansion via the Virtual Boy ES line. This is done using a 256Mbit flash if the expansion is needed otherwise the 128Mbit flash is loaded. If the 256Mbit flash is loaded, that’s 8 times more capacity than even the Hyper Fighting 32Mbit cart. The PCB fabrication is completed and shown below in a two tone black and red. Now just need to load the parts.
And now fully assembled with a 128Mbit flash. It supports a 256Mbit as well as mentioned above.