Ryanair actually orders specialised 737s with built-in airstairs and a few other modifications to facilitate this.
This only really works for 737-sized planes and down, though, where air-stairs are an easy option (AFAIK even A320s can be a bit of a stretch, as they're significantly taller than 737s).
Ah, that depends on the airport. Haven’t been on one of those in a few years; I think Ryanair and friends managed to grab a lot more proper gate space during Covid when the higher-end airlines were practically giving it away.
(Years ago, I was on a Ryanair flight to Brussels airport which used a jet bridge, because it’s mandatory there… But the jet bridge was in the middle of nowhere, served by a bus. Half-convinced Ryanair does this sort of thing deliberately, to live up to their brand image of being quite annoying.)
> but perhaps loading/unloading is not the critical path anymore in turning around the airplane.
It _definitely_ is, at least for short-haul stuff.
There was a company about 15 years ago that developed a double ended jetway so you could load and unload from the front and back simultaneously. They said it shaved about 18 minutes from loading and unloading (combined). On the average flight this would be the equivalent of going about 100mph faster for seemingly a simple change.
They installed a few in Denver and I believe in Calgary. Unfortunately one in Denver had a problem and collapsed and hit the wing of a plane, and so they ripped them all out and no one ever tried again.