The next release of Fotrs Ultimate (current v0.63) will have Fleet Boats and Pig Boats filling up the harbors in docked or underway positions. These are the "static" subs....no crew on deck:
The Fleet Boats will update their conning towers as dates allow.
Our "Mission Expert" propbeanie has been adding them to the various harbors as appropriate. Actually he's got so much harbor traffic, you'll need a traffic cop to get you out to sea!!
New release of an updated version is coming soon.