Thanks everyone for your replies and thoughts.
Like I said, currently it's just an idea - although I do intend to refurbish one CPP2 motor unit for myself, replacing the rotation motor, pump and the electronics, just to see how difficult (and expensive) it would be.
I'm doing this together with a friend who's very good with electronics, and so far we've decided that the whole story should not be too complicated.
Once we get one of those beasts done, I'll have more info and more detailed price and, possibly, available options.
Anyway, I'd still like to have your opinions on the setup and possible improvements.
I've been thinking about adding a programmable timer with audible alarm(s) (like the new CPP3 has), but it complicates matters greatly. Besides, having a separate timer is not a big deal (smartphones come to mind, although for that purpose I still use a Palm Pilot )
The majority of electronic parts should be replaced by PID temperature control unit, plus the module for setting the rotation speed.
That one redesign on the link in my first post (on Large Format Forum) got me thinking about the whole thing: given the average age of these processors, I am of the opinion that the best thing would be to replace everything with readily available parts, i.e. both motors and the electronics.
I'll be able to tell you more in a week or so, after we've done some sourcing for the motors and other parts.
In short, I'm not offering anything yet - currently I'm just trying to see if there is any interest in such a service, at the (tentative) price I mentioned.
In the meantime, please feel free to suggest anything else that you might think of, including the preferences (e.g. everything contained in the existing motor unit, or with a separate control panel, like the one in LFF link I provided in my first post...).