For more variety in missions, you can research "bounty hunting".
It's a crucial implementation and offers alot of missions and a token-system to earn prices and technologies.
Also underwater and space missions.
And all those shippings you can try to attack. Just use the tools the game offers.
Thanks i was aware, i was only suggesting some more without research needed (like the warehouse wars ones); at least i hope bank robbery may become an early one ☺
Edit: in the last relases im not able anymore to ground assault civilian ships, maybe of the changes? Undersea and sapces missions i never "reached" them, since these are advanced ones, plus the mod is too difficult for me i doubt will ever play these
Edit: as for medical another idea: vodka may have three shots like atom beer and first aid kits may have their durability shortened from 10 to 5 but also painkiller and stimulant added with 5 shots, only grog barrels shold earn the refilable status but are heavy and hence not easily handled in battle..to keep things difficult! ☺
Sorry again for the load of typos!