I saw a setup for a ~30' boat designed to do the northwest passage
that had 3 wheels. Two of the wheels were chain driven with enormous reduction ratios and 2 people would pedal to get the boat clear of the water/ice. To steer, they would pedal at different speeds. There is no reason why you couldn't do something like this or even replace the people with electric
or hydraulic motors.
How much of an engineering/fabricating background do you have? If you are a competent mechanical engineer
, you could design the legs pretty easily. Depending on how automatic you want everything to be, you could keep everything relatively simple. Keep in mind that this will be expensive to design and build, possibly more than that dinghy.
My biggest concern structurally would be whether the hull
could be supported by so few points. Unless you put fancy suspension on, you will end up with situations where 1 point is carrying most of the load. With a cat designed from the ground up, this would be easy to factor in but might be a difficult retrofit.