A lot of these suggestions are stations that don't really cost an awful lot to keep, which is why they have been kept. Dolgarrog for instance is already there (just rebuilt, albeit as something about as quaint as a 1960s tower block) and so serving it as a request stop is of little penalty. Roman Bridge is basically pointless (essentially serving one house) but hardly costs anything to keep. Sugar Loaf is similar, as is Berney Arms - as long as the route is needed it's no sweat to serve it and it requires minimal maintenance.
It's probably worth looking at what has been closed in the past - smaller stations like Roade*, Barton and Broughton** etc on the WCML were lopped because serving them was inconvenient as those sections of route have no stopper. So it's this sort of station that might go, give or take those where there's another reason to close e.g. a footbridge being in an unsafe condition (see Polesworth). So we would want to look for stations where there could be a whole service withdrawn, a whole line closed or improved in efficiency if they were closed, or where the running time is such that you can't do clockface but could if one or two stations were lopped out (the Swiss often close stations in this sort of situation).
There are certainly some of these on the Marston Vale, with EWR's proposal to reduce to five. Others might include the likes of New Lane, Bescar Lane and Hoscar which are a barrier to providing a regular-interval half-hourly service from Southport to Manchester and are barely used at all. Cheddington is a bit of a faff (and requires a new platform) but is probably too well-used, and I'd expect to see development there at some point. If we consider that Manchester Airport is always going to have long distance services, Mauldeth Road, Burnage and East Didsbury are a faff - the former two served reasonably by bus, the latter has a tram stop and frequent (if slow) buses, though I doubt they would go as Burnham would make too much of a fuss about it. Glazebrook serves basically no purpose but again development might occur around there at some point. Capenhurst gets in the way on Merseyrail but again there are developments planned. There are probably surprisingly few - arguably Beeching did a good job!
One that could happen is the Conwy Valley south of Betws if there was a major collapse in the unlined tunnel. That would allow a two hourly service with one unit so would have upsides. Perhaps it's a good example of operational convenience from a closure.
* It's sort of a junction, so "Roade Junction" would be an entertaining name
** Reston is almost the same as these two...