The real world option is just a little tweaking of the existing plan they had and its execution.
 
 

Before the actual D-Day navy people forced the bombers to wait a few seconds before releasing their bombs, so that bombs would not be dropped on the navy. As a result the bombers (arguably) missed the beach completely.

So if there was no delay before dropping the bombs, the beach could have been plastered. The bombardment was intended to bash not just the machine gun pillboxes but also the artillery.

Before the invasion the British had an excercise. The weather was challenging, and the duplex drive tanks could not handle that. As a result, during D-Day the British released their duplex drive Sherman tanks relatively close to the beach. American forces released their duplex drive tanks relatively far from the beach. As a result, most of the tanks sank in the choppy waves.

If the American tanks are released close to the beach, the troops coming ashore would have their massed firepower and armour to help them get off the beach. This is not quite a panacea. Some tanks would still sink, and the rest would arrive whenever they manage to arrive. Once they come to shore they could and would be shot at by anti-tank weapons firing down the length of the beach, with not a lot of manoeuvre options.

During the actual D-Day on Omaha the landed troops were pinned down and massacred for hours. Eventually destroyers came very close to the beach, even almost scraping the bottom, to pound targets. Coming close meant that visibility in that smoky environment was improved. There was some wrangling to allow the destroyers to do this. The guns on a destroyer are powerful, and this certainly helped the troops to make it off the beach.

For a tweaked D-Day plan, there should at least be plans made for the possible use of destroyers for close support.

I would provide a tarp for the landing craft to prevent them being waterlogged. I would also provide ginger to the soldiers to deal with seasickness.
 
 
 
 


 
 
 
 

a forum post

some juicy details there