Plausibility Check: Sealion in 1941

[Onkel Willie]

This is the second unmentionable seamammal thread I've posted. I don't know if there have been threads on this before since the search function isn't too great, but WI Sealion had been postponed until 1941? Suppose Hitler gets it into his thick skull somewhere around 1939-'40 that Britain is prepared to fight for a long, long time for Poland (at least if it's left up to Churchill) and orders preparations for Sealion to commence and orders to gear for this invasion after France is defeated. The OKH and the Kriegsmarine tell him that they can't pull it off because their navy is too small, they don't have landing craft and because the Luftwaffe of that fatass Goering couldn't establish air superiority over southern England. Goering is radically demoted and others like Ernst Udet and Erhard Milch takeover (de facto anyway).

Both Milch and Udet know the numbers and urge Hitler to switch to total war production if he wants to knock Britain out by 1941 which leads to increases in production, not only in the Luftwaffe, but in the Wehrmacht and Kriegsmarine too. The navy gains more funding to build landing craft and assorted escorts such as destroyers, corvettes, light cruisers, U-boats and S-boats. The H-class battleships are put on hold indefinitely to use their 16 inch (406 mm) guns as coastal batteries at Calais and Cherbourg. The invasion is set to begin between April and July 1941.

Bear in mind that I fleshed this scenario out in five minutes. Is it plausible or not?

btw, we will assume for the sake of this thread that Stalin does not go bonkers and invades in the east as soon as the first German boots step down in Britain. If he invades, it'll be in '42-'43.