OK. Here's a thought. I read in one of these posts that someone found a date string with all the dates listed sequentially. Now my technical knowledge of plug development is limited, but try this theory:
Assuming that the Nova engine accesses this date string to advance the date when you jump, you could theoretically create a second string, rearranging the dates in reverse order to make the dates go backward as you jump.
By finding some way to access either string at will (perhaps a misn resource?), you could move "forward" or "backward" in time x number of days.
A plug this technical is WAY above my current ability, and may not be possible. Some of you out there would know better than I, but if someone can take this idea and run with it, I'd be interested in seeing the final result.