As explained at category:Unproduced Doctor Who TV stories, no special dab is needed because, thus far, there's been no conflict with produced stories in the same medium. Disambiguation is there to serve one function: to disambiguate. The Fragile Yellow Arc of Fragrance (TV story) is already clearly distinguished from The Fragile Yellow Arc of Fragrance (audio story), so no (unproduced TV story) dab is needed.
(Also, the {{unprod}} tophat, brought up above, has been around for nearly 9 years. It's not a new thing to be invented; it's been doing its job all this time, just fine.)
As for the merging idea, stories adapted from unproduced originals, like The Song of Megaptera, are adaptations, ie. separate productions (sometimes even reworked for an entirely different cast of characters). And Shada (TV story) is not Shada (webcast), Shada (webcast) is not even Shada (audio story), and none of those are Shada (novelisation). Adaptations have their own separate histories and on this wiki constitute distinct stories from the source material they're based on. The story of the original is not just a footnote to the audio story or the novelisation, even if the final product never came to pass.