Tomi, you have a knack for taking something that is "good enough" and showing that it is only the beginning of something a thousand times greater. You could end up with a virtual U-Boat that doesn't even need the game to be appreciated. Have you considered releasing it also as part of a stand-alone tourable U-Boat model? This is worthy of a commercial product, perhaps for a U-Boat museum somewhere!
Your mod, your way, sir.
Don't yield to pressures to depart from your vision. And decide for yourself where and in what way it gets released. No matter what you do some will be happy and some won't. Make the decision on your own anyway. That's how things get done: by people with the courage to be found in the same room as a decision. Do it your way and make no apologies.