I have had thoughts along similar lines.
It probably has something to do with being bored out of my brain for the last 6 weeks, recovering from a shoulder operation but ....
I was thinking of a blend of a surfboard and a twin tip, shaped from a surfboard blank.
Most twin tips have thin square rails. A few like the Jimmy Lewis Model 3, Underground SRF etc are close - they have a type of surf shaped rail but are still very thin like a snow board.
I would have it shaped with surf rails, a sharp edge near the tips becoming more round and soft towards the centre of the board. It would be shaped like a surfboard out of a blank and then glassed. The thickness could vary but basically 1 1/2 maybe 2 inches (depends how many pies I eat over the next 6 months)
This would allow the board to have more thickness than a traditional twin tip and hence more floatation and hopefully not be as power hungry as a Hammer or Jimmy Lewis type board for a similar length.
The bottom shape would be a single concave in the middle for speed blending into a slight double concave or vee through the fins.
You could have it set up with ether a twin fin setup on both ends to be loose or a thruster fin setup on your back foot and twin tip setup on the front foot like a Cardboard Wave. It would be pretty symmetrical so could be ridden either way like the Wave.
I believe the advantages would be a board that gets up on the plain early due to the extra thickness/buoyancy and a better carving quality of a surfboard.
The disadvantages, less strength/durability, and less pop due to the surf rails.
(I have a Cardboard Wave but it doesnt quite do what I want it to and I find it a little long for a twin tip. I am still yet to dial it in. I am not sure why and am still playing around with the footpad placement - maybe next summer I will sort it)
Anyway I would be interested in any feedback

I may even start shaping one in the next few months.