Actually, it would be easier to create a "coupe" out of a roadster. But no question is too far "out there". After all, a fairly large number of Ferrari Daytona coupes from the early 70's have been turned into "Spyders" (roadsters) over the years. But one shop that was doing the custom "chop jobs" said they were going to keep all the Daytona roofs they cut off, just in case.
But a Roadster would be the best place to start, if anybody wanted to attempt to build an actual "T-Top".