The thing to remember is how to combine gameplay with realism. I see post all the time complaining that an aircraft or vehicle model isn't modeled correctly. HT would have their work cut out for them because if you have the ability to change speed on the sub, the skimmers would start demanding that they have the ability to change speed also.
EDIT: I don't feel that a person "driving" the sub should have the ability to "see" surface platforms that are far away. To keep the realism, they shouldn't be able to see the fleet until they either
a. see while running on the surface
b. find it thru the periscope and
c. find it by using the sonar hydrophones
Then we get into the whole resupply situation. How many torpedo's will the sub have initially and how close to a friendly port will it have to be in order to resupply? Don't forget, subs had AA also to protect against planes. Another thing to think about is if the sub is sunk...they HAVE TO start at the port...no starting 5-10 miles away like a vehicle can. If HT or anyone has any questions, please feel free to pm me.
Here are a few things to look at concerning WW2 sonar...
http://www.zerobeat.net/submarine/sub-sonar.htmlLook at the station to the right with the two circles in this picture.
http://www.maritime.org/tour/img/tctsteer.jpgHere are a few more b/w photos of the sonar units.
http://www.maritime.org/radio-wca.htmhttp://www.maritime.org/radio-jt.htmhttp://www.maritime.org/radio-jp.htm