If we create an imaginary Air PuddleJump at it's finest, greatest and most competitive, it might be have been something like an amalgamation of Manx2, Air Wales, Air Southwest & Scot Airways at their peaks
Air Southwest didn't operate Puddle Jumpers, they operated 50 seaters!
The history behind their operation was Brymon operated a HPR7 NQY/LHR/NQY and a DHC6 PLH/LGW/PLH.
Brymon ordered 4 x DHC7's and to part finance needed to sell the HPR7, two DHC7's operated out of ABZ whilst the one south-west based DHC7 started a PLH/LHR/PLH route.
Then, when the HPR7 went to Janus Airways, for ONE SEASON they combined the NQY & PLH LHR routes with the one DHC7 until the 4th DHC7 arrived the next season ... it never arrived.
The NQY punters were in uproar, they'd lost their direct LHR/NQY service because it was routing via PLH, similarly the PLH punters were in uproar because to fly PLH/LHR they had to route backwards via NQY.
Alas, what was to be for just one season, Brymon was taken over so the memory of what was supposed to have been was lost, the DHC8 was launched as a 36 seater where separate routes could have been re-introduced but Brymon went for 50 seater DHC8's keeping the routes combined and Air Southwest never saw the light, all their maintenance approvals were DHC so I presume would have been costly for them to go for another aircraft manufacturer's type.
Air Wales were a puddle jumper when they operated Do228's, not when they operated ATR42's, and it is said that they might still be going had they stuck with Do228's ... They'd certainly be operating the Angelsey route.
Airports and routes are not being served, are being lost, because manufacturers have, in most cases, stopped manufacturing 'Puddle Jumpers', sure as a rule of thumb the larger the aircraft the cheaper per seat it is to operate but there remains a requirement for lesser sized aircraft.
DHC stretched the 8 some two or three times to then cease production of the smaller variants, good on ATR, they stretched the 42 but they've kept their smaller variant in production, BH stretched the Islander but kept it in production, if it's all about size then from the 737-300 why did Boeing develop the lesser sized -500 and ditto to Airbus who stretched the 320 but also went smaller with the 319 & 318 and so on.
When I used to travel on business, regularly from BHX, it was great, for my trips to MXP or FCO Swiss operated 3 times daily, for CDG I recall AF/Cityjet some 3 times daily, for my trips via AMS KLM operated some 5 times daily with different types (F70, F100 and different sizes of B737) depending upon the time of day, I could travel at times of day when I wanted to travel and not when a larger aircraft operator might have dictated that I needed to travel at the time they decided.
I used to regularly travel with Austrian from LHR, invariably they operated A321's but their mid afternoon service was operated by a F70 and to regional airports in Russia and Ukraine they would operate CRJ's, when I flew with MALEV from STN going out it was a B737 but coming back a F70, MALEV operated CRJ's also, the times I flew BHX/DUS/KBP with Lufty, it was 50 seater CRJ's all the way there and back, the route was only viable because of the small equipment they were utilising.
So even the big boys develop routes with smaller aircraft such as CRJ's and F70's and there are regional airports in and around the British Isles missing out and/or not being served because of a lack of appropriately sized aircraft.
I read that Do328, both Prop and Jet, manufacturing is to recommence so that might make for an interesting order book!