How long did the US expect the Japanese to fight on before throwing in the towel? And was the invasion ever war gamed out like Sea Lion was?
Not sure: the material on the war game doesn't mention projected casualties for V Amphibious Corps. Japanese casualties, though, would have been extreme.
In the game you land 9 marine regiments on the middle of Sendai Beach, 9 army regiments on Tsuno Beach with the right flank on the edge of the objective line and 9 more on the north end of Miyazaki Beach. The marines bull their way into Kagoshima (it is a valuable objective) whilst the army expand their enclave.At Tusno, that may have worked. However, at Ariake Bay and Kushikino, there really was no other choice. You want to open Kagoshima Bay and get the airfields around Kanoya? Land where XI Corps and VAC were supposed to in the OLYMPIC plan.