How are you going to run a more frequent service on the S&C if you dont want to start with a simple shuttle from Skipton into the Dales? Good luck finding spare paths from Leeds to Shipley, for start.
...since youve pointed out that there isnt a single spare 153 in the country (and you dont want shuttles from Skipton), Id be interested to know how you are going to improve journey opportunities for those wanting to get from the Dales to Leeds (?).
I doubt that there are any spare paths at the Leeds end (six EMUs an hour through Kirkstall plus lots of random slow freight plus the current bi-hourly S&C services plus a handful of awkwardly timed Lancaster/Morcambe services), which is why I was suggesting a shuttle to/from Skipton, to connect with those regular EMUs to Leeds/ Bradford (off topic - funny how often I read that Bradford needs better services to places south of it, but you never see people suggest services from Bradford to Morecambe/ Settle etc).
So, if you want to increase the number of journey opportunities from the Settle area to Leeds then you can either find some spare Sprinters with good acceleration to run in the path of a four coach high density 333 on the Airedale service, or you can hope for something simple like a spare 153 to shuttle from Skipton to Ribblehead. Its not glamorous, its not as exciting as running 125mph stock from London up the S&C, but itd fill the gaps between the current bi-hourly S&C service and would be a good starting position to assess whether theres much more of a market out there. Who knows, it could even be upgraded to a 142 after a couple of years...