Ok, so don't attach anything "permanently".
What I'd suggest would be a very "bare bones" board, just one rather robust MCU, a good power supply, IO buffers in easily replaceable configuration in case you burn them, (i.e. in sockets), replaceable quartz (in case you need slower/faster board), the basic means of programming the MCU (MAX232 type chip + serial socket, or whatever it uses), and a reasonable "bus" socket, say, 40-pin like for IDE/ATA devices, driving all interesting signals further, for stacking different boards on top of each other. Possibly an address decoder on some data lines as well, but I'd rather put it on a separate board. Then create attachment boards as you see fit. DAC/ADC, display, infrared etc. You can create a few "blank" attachment boards as well, for experiments, new parts etc. This way:
- anything broken is easy to replace.
- removing failed designs is as easy as pulling the plug.
- You are not limited with board space - you can always add more boards.
- If you want to replace obsolete part of the system, it's very easy too.
Just make it into kind of "lego bricks", easy to expand, modify, scale down and repair. There will be possibly just one serious problem: Line noise, ringing, propagation delays, line voltage drops and all those kinds of nasty effects present in decentralised design, limiting maximum speed and forcing you to stuff every empty hole with capacitors to get rid of them - but a "generic" development board wouldn't help against that much either.