suggestions
 

- lock the development team for a month and make them play silent service for the ZX spectrum every day

- realistic traffic patterns and convoys (small merchant convoys with few escorts) for random encounters. Convoys follow routes based on historical traffic patterns for each geographical region. (Cities, naval bases)

- large, heavily escorted convoys mostly reported on the radio. These would follow known long routes to and from Japan or major bases. Wolfpacks on these cases.

- realistic damage model and damage control crew

- Role of the player is of the submarine captain. Don't need to impersonate the other crew members (or actually see them inside the sub)

- Sub simulation is IMO more about strategy than action, so Seeing the a highly detailed interior of the sub is more for the action fan

- Realistic graphics outside the sub is essential. (Fog)

- Save game MUST work

- Enemy AI (That takes geography into account. Don't want the targets to just beach (at least in daylight). It would be too easy.

- Ability to play both US and Japanese. US subs sink patrol and sink ships. Jap subs do specific missions (spy, transport, scout, etc). The way it happened in history.

- Accurate depths

- More accurate modelling of port activity. It shouldn't be easy to sneak into Truk lagoon for example (There were specific channels and they were all guarded by escorts)

- Historic events (being in the wrong place at the wrong time ) with radio messages to go with that (the game can teach some history, and kind of makes you feel there)

- Make the missions and campaings the more random possible. Scenarios tend to be boring.