I think Sea Lion is worth it, but it has to be a complete Axis operation. Japan has to attack America turn 1 and put their foot on the Americans throat in the Pacific. Crush the Hawaiin fleet, take out Philippines. Japan then needs to keep most of their focus on America the subsequent turns, making sure to hold Hawaii and beating the Americans back to their own sea zone. Taking a smaller fleet and clearing out the money islands in the Indian Ocean is the 2nd objective, to start collecting enough money to support this.
Germany and Italy then must focus solely on Sea Lion, with air assaults on the Royal Navy and bombing raids. Italy must give up on Africa for the time being and buy to stock up for the impending Russian invasion. Germany goes all out for sea lion too while also preparing somewhat for the Russian invasion too. By turn 3 London should fall to the Germans.
If all goes well, it puts America in a huge dilemma. Help in Europe to get London back? Or the more immediate threat of a rapidly growing Japanese empire that is collecting almost the same ipc as America.
If America chooses to get London back, it’ll take a few turns to get the necessary resources to be able to accomplish, while sacrificing in the pacific where Japan goes all out on America and could be sitting on their doorstep for an invasion.
If America chooses to spend most in the pacific at the more immediate threat, the Japanese empire should be strong enough financially to be able to support such an effort for a long time while grabbing money in china, Russia etc. this scenario Germany now is only fighting a one front war and can put all resources to defeating Russia. The Russians will make an immediate push to start, but Germany should regroup, concede some ground then drive them back. Use the transports wisely to put a threat to Leningrad at all times.
This is the strategy me and a friend will be deploying in a game that will be starting soon. In my group of friends the allies have been dominant recently winning 8 of the last 9 games. This is something very new as most Japanese players in our group don’t attack the us to keep them neutral while trying to eliminate china, and set up a crush of Calcutta and Sydney.
On a side note we don’t play victory cities. In order for victory, the allies must capture and hold Berlin or Tokyo for a full round for victory, and the axis must capture and hold 2 of Wash, SF, London, Moscow for a turn to win.