> Would another scrappage scheme for FM radios be of interest?
NO; no-one paid me to scrap my analogue TV, or replace my LPs with CDs or HDDs, or my VHS tapes with DVDs/Blu Rays.
> How key is the quality argument?
KEY; there should be a minimum legal bitrate (on digital TV too) and minimum level of coverage. It is not "increasing choice" to cram in so many channels they are all unwatchable/unlistenable, it is REDUCING QUALITY.
> Is DAB the right format?
No. DAB+ is, even if it has to be phased in painfully like HD on Freeview.
> Does none of this matter as we're all going online anyway?
THIS DOES MATTER, because broadcast and online use bandwidth differently. Broadcast costs bandwidth once per channel, so the broadcaster (advertising, license fee) can pay for it centrally. Online costs once per user, so the user has to. Broadcast will always make sense above some audience threshold, where that is will vary over time with technology, but a low general estimate should always be used so services don't get dumped in a temporary pricing shift.
Usage history/experience
I'm 50-odd years old, and a "rational adopter", e.g., I have an iMac but no iPad
I switched exclusively to DAB about 3.5 years ago, and haven't tuned in to FM since. I mainly listen to Planet Rock, Radio 7 (4 Extra, yadda) and TMS on Radio 5 Live Sports Extra; although I can get these channels via Freesat as well, I rarely listen that way at all.
General comment.
The UK's digital everything strategy is a mess, largely because politicians and civil servants are exclusively from the verbal/written tradition (language, History, Politics, Law degrees) and are helpless with symbolic reasoning, which is essential for making technically sound decisions.
It's no good saying "scientists should be on tap, not on top" any more, if you can't do the numbers you're reduced to making the decision on which speaker "sounds like a good chap" or "has the right tie" (or the feminine equivalents, Clare...). If you can't do the numbers you shouldn't be allowed to make the decision — or stand for office in the first place IMNSHO.