1. Remain in WW2 era.
2. Make all basic stations operable by player.
3. Expand scope as to include more WW2 combatants.
4. Global map based on a sherical world plus plotting tools to allow you plotting long trips on said map.
5. Reafirm and/or improve boat <-> sea interaction.
6. Proper reporting/feedback by crew
and finally
7. Hire subsim modders to do the job!