For me, in lieu of an additional generic 'harbour mission', more randomness is mandatory.
People are quick to complain when missions / games have no replayability, but have little understanding or patience with how hard it is to craft these things... so my suggestion is to cram as much depth and complexity into the mission from the outset, so that other than perhaps the 'historical' mission objectives and the shape of the coastline, EVERY single thing else is random. The depth and shape of the ocean floor, placements of nets, mines, escorts, aircraft, observation lookouts etc...
Make it once, but make it as deep and dynamic as you can... give people reasons to replay it.
Having spent almost 2 years inside Star Trek Bridge Crew with missions that claimed to be dynamic, but were on rails with very few choices, and those choices were always fixed, that (aside from bugs and really ****ty game designers/devs) is what killed the game. After you master it, there's nothing left to do.
Expect that you're only going to have the time and money to make each mission ONCE, but you want people to have reasons to keep playing those missions for years to come and still keep getting something from it.
IMHO **that** is what you should be aiming for these missions.. Good luck Neal.
