The only boats that I can think of off the top of my head that could serve such a purpose would be a Tug Boat (the older rounder hulled ones) or PT Boats (ww2 to Nam). while neither has a totally rounded front hull they are the closest thing I can imagine.
removal and replacement of the tower and cabin, and other deck pieces would be needed to make it "flat" like the Gunship and of course replace it with the single Robot driver cabin.
the engines are of course a must, but that would require the addition of the bladders on the bottom.
It would take some time but be possible overall.
That or some conversion of an amphibious vehicle. like a Duck (amphibian truck) or this thing.
a German tracked Amphibian vehicle. removing the tracks the lift engines could be bolted in their place and the upper super structure removed to make way for the smaller Auto pilot cabin. Guns as turrets like the multi laser/lascannon on the front bow. wing mounted weapons like rockets or additional lascannons could be either mounted to the hull and fired from pylons or (in the case of lascannons) fired from turrets maned by the crew in pods that as hung from the deck on the sides.
Hope it helps. I can't find a specific model (as boat sizes are all over the place) though.