For a very light, DSLR-based system, this is a thought:
http://iankingimaging.com/search.php?q=skytracker

How would the mount swing back for start of observations?

It is controllable from various planetarium software packages.

How would it point fine enough?
With a large enough field it would not matter – provided the necessary detail on the DS was observable – perhaps worth a study of the tradeoffs between field size, pixel size and SNR?