Hi, i think its better to start entirely from scratch.
This is a good example for a landing craft, approximatly the required size, around 7m length , 2m+ wide.
I did a rough sketch a while ago, need to search it.
The big differnce is that the new design should have the option to open the sides so you'll get a flush deck.
Propulsion should be inboard electric impeller.
Do you use WhatsApp?