I think that a sea lion could be possible for Germany rd #3.
G1-take Paris, and the French Atlantic coast (should be a minor IC on coast).
G1-attack/destroy the UK fleet (as much as possible)
G1-roll for tech-(paratroopers), but LRA could come in handy
G1-add to German navy/air (maybe a/c) in Baltic (should start w/BB and several support ships I hope)
G1-attack UK convoys that you can, and UK NO’s
G1-start ground march to Russia (to at least set-up def)
It1-attempt to take Gibraltar and more of the UK navy
It1-start reducing UK $ in Africa/Mid East
It1-attack UK convoys/NO’s that you can
G2-move German navy (with a/c) to French coast w/IC (English Chanel) (could also move to North Sea as Germany will have access to it with West German IC)
G2-position German air and left over ground units on French coast that just destroyed France to get in range and board trpts
G2-roll tech again (looking for paratroopers)
G2-SBR UK, to reduce UK $, and air force with escorts/interceptors, Germany may have superiority
G2-build 3 more transports on the French coast tt w/IC (or West German tt North Sea port) to put w/navy
It2-continue giving UK hell w/attacks and convoy/NO disruption
It2-maybe set-up a secondary Italian sea lion as well (just in case) if feasible or meet-up w/German navy if Italy took Gilb.
G3- if it looks like you have a chance to take UK down, go for it. If not you can always back track through the Baltic to attack Russia. You could also go north and land in Scandinavia. So at this point you have options.
UK will be building through this process, and making counter attacks. A Sea lion attempt will ultimately depend on the starting strengths of the German/UK navies and air forces, or their ability to get superiority. Italy could play a part by getting to Gibraltar, and cutting off the UK naval reinforcements. I’m still not sure if you can pull off a Sea Lion w/o paratroopers.