Good Morning Casey,
I agree, a 1/72 scale Gato/Balao boat would be Heaven. But someone over at HyperScale pointed out that Revell of Germany doesn't usually do U.S. subjects. Maybe with the the huge response to their Type VII-C, that they might reconsider. However, if I were a betting man I'd put my money on a RoG Type IX. That seems like the most logical follow-up don't you think? But if it means anything, I'd vote Gato next, then another U-Boat variant.