System simulation

I played around with gnucap a few years ago and thought that the
interactivity would make it "easy" to get it to talk to an
micro-controller simulator. And now when micro-controller simulator
people has joined up with the circuit simulator people on this list I
thought I'd get some opinions.

What got me into this is that it's possible to continue a transient
analasys where it left off after it has been stopped. If I recall
correctly it is possible to change component values around while it's
halted and continue with those new values.

My thought was to create a new logic device that works as an "digital
generator" that can be changed between 1 and 0 from the command line.
The plan was then that the MCU-simulator would interact with gnucap
through a pipe. 

Would this be enough from a gnucap point of view to get gnucap and a
MCU-simulator (gpsim for instance) be able to act as system simulator
where you can simulate your software together with your electronics? 

A second and required step would be to add ADC's and DAC's.

A relevant question is of course if this is useful even if it's
possible? Personally I only simulate small sub-circuits most of the
time. And I haven't really missed a system simulator, but I think that
if I had one around I would probably use it to verify larger blocks on
more of a system level. It could possibly be a tool for SW design as
well for the pre-prototype coding.

Thomas