Plug-n-Play for vintage machines?

[Jim Brain]

Or, I could just make each of the cartridges a single task board, and 
have users either insert and remove them as needed, or make their own 
cartridge expander with switches to manually enable or disable each 
cartridge slot.

Applications could then display screens stating things like:

"I'm sorry, but this application requires 16K of expansion RAM for use.  
Please turn off the computer, insert a 16K RAM Expander or a 24K 
expansion cartridge with the upper 8KB turned off, and reload this 
application"
"Could you tell me what UART cartridge you have inserted into the 
computer?  I have no way of obtaining that information from the 
cartridge itself, so you'll have to enter it in my application."
"We can't find the UART cartridge at $de40.  Since you've no doubt 
inserted it, it is possible you've not set the address range to 
$de40-$de5f.  Please turn off the machine, ensure the jumper for $de40 
(located inside the cartridge shell) is closed and all other are open, 
and reload this application"
"There's a bug in v1.3 of the expander cart, but I can't tell which 
version you are using, so please select and I will enable the workaround 
based on your selection"

Jim