I'm not sure if it is removable or not. If it isn't, you could still work with that; you'd just come up with some sort of socket.
Wouldn't that be COOL to have a cartridge-based Mac?? You loose all of the nice things Apple gave you, but you could bring parts of it back with some excessive hacking. I believe there are COMMENTED, disassembled versions of most very old ROMs like that. You take the original ROM, run it though some program, and it disassembles and adds all the comments. This would be very helpful for Mac ROM hacking.
A more modest project which could be just as interesting would be to take the existing ROM and just modify the startup sound, happy Mac, and background texture. I have done this with a ROM image file and used it on Basilisk II. Unfortunately Basilisk II doesn't play the startup sound, but I have a pretty nifty 1-bit white Apple logo outline with the rest of the screen totally black in place of the happy Mac. Kind of reminiscent of Mac OS X although the black background makes you wonder for a moment if you have a sad Mac! The background could easily be changed to any 1-bit 8x8 texture. Actually I believe I still have that somewhere. You could totally burn it and use it in a real Mac.