The poly count really isn't bad if you only have one or so of these things in game. Perhaps a low poly model could be done, which just shows the exterior and isn't enterable.
For the USN this ship would be a part of an Amphibious Ready Group, which is a small group of ships needed to transport, support, and command a Marine Expeditionary Unit. Amphibious Ready Groups will usually include an LHD (Wasp Class), an LPD (Austin/ soontobe San Atonio Class) and two or so LSD's (like this ship).
Now, all four of the above ships might be a real slow down on a system... if the attention to detail for each one was as intensive as the ship Jafergon has done! But if a low-poly external-only model were used for three of the four, with the player seeing only the insides of one full detail model, well, that might be doable?