just a note that might be interesting.
first of all it seems like the japanese super gameboy 2 works in a european snes without modifcation to the lock out chip (i did the mod first on a switch before trying the cart, only to find it works regardless of the switch possition)
the super gameboy 2 is based on the gameboy pocket, i have actually put the CPU from a SGB2 into a pocket to make a silent quick boot pocket.
it is possible to put a normal gameboy CPU back into a super gameboy, and then booting it using a special cart (nitro2k came up with some code which will get the super gameboy to boot with a DMG chip, then you can just switch the carts after)
not only is it possible to put a link port in a super gameboy (in fact its very easy) but you can go as far to install an arduinoboy inside one, i have done this on my super gameboy 2, and on my gamecube adapter.
lastly, a small idea. the super gameboy 2 has a small transistor which switches on an LED when you are using the link port, it might be kinda cool to have a similar transistor in a normal gameboy