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It all sounds good... good and expensive to make. I am not sure there is a large enough customer base for such a game.
Making a WWII submarine simulator is a delicate balancing act. Make it too realistic and it would be boring. Make it too exciting and it would be less a simulator and more an arcade type game.
This why I, personally, feel the mods have done a wonderful job with SH3 and SH4 trying to get that balance more finely tuned.
I agree we have the technology. I am not sure the demand would be there from a commercial standpoint.
Someone has to pay to make this and they probably want their money back in sales. I don't have the money, that's for sure.
You ask three SubSim members what they want to see in a new simulator and you will get five different answers.