By definition a GT has to have some carateristic that elevates them from "regular" sports cars. Things like comfort, high speed capacity and some sort of luxury are mandatory for a real GT is you ask me. Having a sporty look is somehow relevant, but this one might be more of personal preferences.
So to answer OP, I don't see how a twin can match that unless you totally transform the car. It would become something else and I don't see the point of taking that route with a sub 30K car.
That doesn't mean the 86/BRZ aren't capable of long distance travel without being adequate. I've done two trips of 10 hours straight in 2019 and I was very surprise how good it felt. No disconfort or road noise annoyance what so ever. Again this must be a matter of personal tolerance because my mother in law couldn't stand being in my 86 (mostly stock), after about 10 minutes she was done with it.
Adding some soundproof materials and the quietest tires available are the only things I would do to make it more of a "GT"...but I won't.