Of the one-train-a-day, each way, halts on the North Cotswolds line, I'd expect Finstock (despite its proximity to Charlbury - although it would really need a car park, and probably better promotion of the reasonably decent bus service it has) and Ascott-under-Wychwood to have quite some scope for growth if the train service became more usable. (That Ascott is on one of the re-duelled stretch of the line may help: the new platforms there are possibly lengthier than at the other halts, too). Combe probably doesn't offer such hope, though: the station is both remote (in terms of its micro-location: on a country lane some way outside the village from which it takes its name) and rather close (for drivers) to Hanborough.
Since the redoubling of Charlbury - Ascott, I'm at a loss to see why the short workings to Moreton-in-Marsh haven't had stops at Ascott and Shipton added in to see if there is any off-peak demand at these stations. There seems to be sufficient lay-over time in Moreton to allow for the extra stops in both directions.
Finstock? This is a joke, right? If someone at BR hadn't cocked up the paperwork in 1994 it and Combe would probably have closed back then. A change in the law on closures in the meantime meant they didn't bother trying again. It's a mile or so from the village (about the same distance as Combe station from the village) at the bottom of a steep hill, so effectively zero walk-up potential and highways would have kittens about the idea of a car park access on the road there, never mind it's also in the Cotswold AONB so a lot of tarmac and lighting wouldn't go down very well...
Ascott is a different matter, right next to the village and with both platforms able to accommodate three-car Turbos - which is an issue at Shipton, as the up (Oxford-bound) platform only just squeezes a two-car Turbo set on, so the Moreton turnbacks, which are operated by three-cars, cannot call in that direction and there aren't enough 180s with FGW to replace the turbos on those services as well as the trains to Worcestershire to provide selective doors and solve the short platform issue.
There is talk that changes may be afoot shortly for services at both places but off-peak stops aren't all that's needed. At least one more peak service in each direction is vital, as the present halts service is not a great deal of use unless you need to be at work in Oxford at 8.30am, though I surmise this kind of improvement is going to have to wait until any post-electrification recast of the GW timetables, as there simply isn't any spare rolling stock available at the moment.