In his Channel crossing William the Conqueror was landing on a practically undefended shoreline, and with plenty of time for his troops to recover if the voyage turned a bit choppy; he was not in a situation where he needed to worry about landing highly seasick troops, whose tanks it may have been impossible to use in the assault if the seas were too rough, in front of Hitler's 'Atlantic Wall'.
Nor did William the Conqueror didn't have any airborne element to his landing to worry about strong winds or low-cloud playing merry havoc with...
First, in 1943 the Atlantic Wall was noty yet fully built. That work only really got swerious when Rommel took command im early 1944. This time the landig is most likely to be planned for September 1943 and might well not be the main show which is likely to be in Southern France (Italian invasion cancelled or reduced to a secndary operatn, perhaps near Rome) The Normandy landing at this time was planned using only 3 divisions and in TTL it might not even include airborne troops who would go to what wuld now be the main attack in Southern France. A September invasion of France with the main weight of the landings in Southern France with Italy cancelled or dramatically reduced (taking advantage of all the landinfg craft in the Meditterannean theatre fr Sicily and the originally planned invasion of Italy) would be quite feasible and culd well have been considered had circumstances changed sucjh as o take advanantage of more severe German defeats i Russia bringing about a possible German collapse situation.
While the discussion of Western Allied plans and options is interesting and has relevance at this time it delays write ups covering the developig situation in Russia which is neccessary for the further development of the timeline. I need to complete the coming German defeat a Kursk and its' impact on thee rest off the 1943 summer campaign. Then we can look at the impact as regards a Generals' plt to overthrow Hitler and Western Allied strategic decisions based on the changing circumstances. Without wanting to give too much away right now all this will tie up eventually with a radically altered coclususio to the war