From the guide, switch out the green HBT trousers for US Mustard Trousers, and the Ranger diamond for a Big Red One patch and that will be fine.
Not every Yank had a thompson, only usually NCOs or Officers had them. Basic rifleman would have had an M1 Garand or a Carbine depending on their responsibility within the platoon.
right US on the cheap. Forget the kit carried on DDay. It was common place for infantry to have just fighting kit. So lose the backpack and go belt order. Many pic's of GI's with just either a pistol belt or garand belt. The M41 jacket was reasonably universal, HBT's are fine for a cheap kit. As for rank, its not really necessary. As for weapons, really until someone see the light and make an aeg garand, the only option is the thompson. Start small and work up. Enjoy.
So lose the backpack and go belt order.
Really? The Haversack is considered part of the "Fighting Order" as it contains your essentials, tools for digging in, eating bits and bobs!
For airsoft though you're right, I wouldn't consider buying the Haversack for a starting impression, they're heavy and cumbersome and offer little advantage in an airsoft game. If you're looking for basic belt order, you couldnt go wrong with a belt, water bottle, carlisle pouch (if you wanted to put things like medic bandages in) If you have a pistol there is always the holster and colt .45 mag pouch. For infantry, you'd be 'more accurate' with the thompson mag bag, however, until you so wished to get it, the 3/5-cell thompson pouch is fine