My 2 cents, if you're talking about the car stock its a hot hatch and not in super car territory in the least. It's been said in the past 4 pages but "super car" means something different to everyone, but I think some standards are:
2 seater? 2 doors? How about consideration for aerodynamics, engineered to directly compete with other similar cars in it's price range (though there is a $$$ disparity between something like the NEW NSX and say a Ferrari 488), WOW styling, NOISE, rarity (again, not a great example on something like a Corvette Z06, but the ZR1 might be a better example) and to quote Doug Demuro, a "cool factor". Also, a "super car" sharing 90% of it's parts with a 170hp and all electric variant isn't common. I'm looking at you Hellcat/Demon.
That's not to say the R doesn't compete with cars in it's class, or that it isn't well styled, but VW probably didn't wind tunnel test for a 190 mph top speed, in the US at least they are all 4 door, 5 seat, practical hatchbacks. And if we're honest, the noise they make isn't ever going to be confused with a Lambo or otherwise.
Now when you mod an R, how far do you think you'd have to go to get to super car levels? I don't mean just measurable performance, but the whole package? I'd be lying if I said it's possible, I don't think it is. It's just not what the platform is for.
What is possible is making a wildly fast, incredibly capable, reliable (all things considered), practical car that will dance with the best of them. It's still going to be a Golf though.