Yaqube seems to have been able to overclock the 68sec000 to around 56 MHz with the aid of low latency ram. This is something that would be interesting as well since it apparently would make the minimig cpu perform about the same as a 030 at 25 MHz.
16 megabytes of physical onboard memory would probably be good too if it was possible. That way you could have 10 mb ram and 512kb rom and also have a bit of extra memory to spare for other possible future expansions.
