I saw another post that has to do with an LVT carrying a Jeep in the back... and I thought why not a DUKW (Duck)?
taken from Wikipedia.com:
"The DUKW, popularly called the DUCK, is a six-wheel-drive amphibious truck developed by the United States during World War II for transporting goods and troops over land and water and for use approaching and crossing beaches in amphibious attacks.
...the DUKW was built around a conventional six-wheel-drive military truck called the CCKW, with the addition of a watertight hull and a propeller. More than 21,000 were manufactured."
What do you think? Could carry troops or supplies... launch from a CV and wade slowly through the water, and then zip into the town as fast as an M3? It would not take much away from the LVT because the LVT would be a bit harder to kill due to more armor... This way you'll have a choice, more speed... or more survivability.
Some pictures here:
http://www.olive-drab.com/idphoto/id_photos_dukw.php3
