You just described inspector gadget. You will want sealed wheel motors and sealed batteries to keep the elements like water out or you will wind up with a lot of dead fish floating around you the first time you take it into the lake. Of course with everything sealed up it will be a challenge in figuring how to dissipate the heat. I do not under stand why you need to expand the length and width of the vehicle. It would probably be better to pick a specific size and put the extra engineering into suspension and body flexibility.