Someone did it, accelerator and all. See this thread on Amibay:
http://www.amibay.com/showthread.php?t=570
Extending the joystick ports is fine, they are designed to be on a long cord.
Putting the computers bus on the end of some slightly different length cables which could affect slew timing and picking up interference a long the way, is slightly pushing it for me.
If they'd made a pcb with a male and female connector that allowed the accelerator slot to double back on itself then I might go for it. Trapped heat will be a problem though.
At the end of it you still have an a1200, but now you're missing the numeric keypad.