Why not a 225PS Diesel to sit above the GTI and GTD? It would be an "R" - not competing with the GTI at all. Be interesting to see what they could do about the price though considering how well specced the GTD already is. The extra turbo is realistically only worth an extra £800-1000, maybe add the e-diff and bigger brakes of the performance pack for another £700 and extra special seats adding £500 to £1000 depending on whether they're like MK6 GTI seats or full blown recaros to make a £2000-2800 premium over the GTD? Not forgetting possible 19" wheels as standard.
The pictures of that R don't look as good as the GTI IMO. Would I pay an extra £3k over a GTD for an RD? Nope, i'd get a GTI if the difference was that much and the combined mpg dropped to 55mpg. I'd pay an extra grand over the GTD purely for the perfromance hike, not wanting all the superfluous extras, but i'm doubting VW will make it that easy to own one.