Is there something in the trade and commerce system (I am still reading through my T5 CD ROM) that could be used to come up with this? How often does a ship come through a given star system? Is it based on Ix, Ex, RU, starport, TL, Pop, Trade Classifications, trade routes, or, more likely, some combination of all of these)? I would love to have an automated way to determine this ... plug all of the information into a spreadsheet along with jump distances to all neighboring worlds, and determine how long it takes to get from world x to all worlds within six parsecs of it. Repeat for the time it takes for the message to get to the next world, and so on.
Cheers,
Baron Ovka