Re: Be careful what you wish for!
It's been pointed out that Ofcom requires 999 to work in the event of a power cut to the premises. ... How do we manage this with FTTP?
Bt have already (IIRC) run trials where they've converted entire villages to fibre-only. The fibre is terminated into an NTE which includes optical interface, bridge to data service (presented as an ethernet port IIRC), and an analogue terminal adapter - plus backup battery. Being an integrated unit, it should be reasonably easy to remotely detect battery state - though I don't doubt that getting end users to swap the battery will have "some issues".
If you just work on needing the service to make emergency calls, then the whole NTE could be powered down except for providing line voltage to the POTS port. If the user goes off-hook and dials an emergency umber then it can power up the required stuff to make the call.
Thing is, these are all "solved problems" where solutions have been worked out years ago.