I seem to recall a mod I used several years ago which made all towns with boat travel available from each shipmaster and all towns with silt strider travel available from each driver. Does anyone remember this mod and what it was called?

I do. It was two mods simply called http://mw.modhistory.com/download-11-5167 and http://mw.modhistory.com/download-56-5170. I still use them to this day.

Sounds very much like this mod (All Destinations).

http://mw.modhistory.com/download-53-12809