Have several amtraks on the beach which serve as spawn points, with usable static machine guns which can be used to cover the advance and once the beach is taken the amtraks can be abandoned. The men would go over the side or out the rear ramp depending on model and fight forward covered by a few machine gunners and perhaps scripted naval artillery while the Japanese try and suppress them with their own small arms and artillery. I don't see a way in which you could have the amtraks constantly returning back and forth as they did in real life, picking up marines from Higgins further out.
Or perhaps the actual area of beach could be very narrow, the area assigned to one Company.
I like this idea a lot. Because the beaches weren't often defended except for artillery, why not just have, on a few levels featuring landings, the marines spawn from stationary amtraks until they get inland a ways?
I read that each one can hold 24 troops. If there were 2-4 on the beach, it'd be believable that 32 respawning marines could jump out of them over time.
Though I do think, especially with such a respawn system in place, there should be a map or two with beach fighting- Peleliu would be amazing. Maybe the map itself would go more inland than, say, a D-Day map, and
the defenders can't respawn until the first objective is taken (thinking like countdown). This way, the attackers can slowly whittle away the defenders and advance realistically, and the rest of the map can be more traditional.
Having them drive up to the beach in the beginning would be a lovely touch, especially if they were human controlled (or in some way unpredictable game-to-game)
I must say, though- non-landing maps are equally important to me. So much of the interest in Pacific maps comes from their variety- jungle, coral, mud, ash, caves.