well it is KISS.
just have defenders fire first in every round and remove loses then attackers fire.
for more realism…
You can also limit the number of units landing each round limited by the IPC value… so in france you can land 6 units 1st round, 12 second, 18 third.
The attackers cant get all the pieces on the beach in one load.
also cost the attacking player one IPC for each land unit used for this purpose. ( this is not a picnic son)
Another thing is to roll a die for sea conditions. 1-3 you can land, 4-6 you cant. Its not like "hey lets invade today… hows the weather?.. why do you ask?.. isn’t it enough that we just decide we are gonna land 1 million men today with no care in the world?.. To me this is asinine that they don’t have something in the rules to cover this.