There is ZERO reason why this could not be done.
We have lvt's that go from water to land.
HTC has a boat that can go from water,to the air. "was used in a special event, like the rv-8 and santa"
Its code guys, the objects shape means nothing.
If hitech wants something to fly, all he has to do is put a little numeral by the code saying "im a plane, or a boat, or a lvt or a new type of craft"
Airplane- 1
Gv-0
water- 1
land- 0
"1 being On 0 being Off"
.ect
"Of course i dont know the exact code,but this is just my guess looking at other game code's"
Basicly, if HTC wanted too, it could be done.
The water would not need changing, the only thing is the craft would need to be made to fly, but not be able to land on the ground "without damage" and of course it would need to land on water.
Like most games tho,the largest battle would be making the model and geting everything with the flight model correct.
"Throws two cents"