There simply isn't the volume of traffic on either route to support the kind of thing you suggest - if there was, then FGW▸ , and BR▸ before it, would have been running timetables with the mix of trains you suggest.
The proposition that you should bypass Gloucester is just bizarre if you're trying to make an hourly London service pay its way.
Perhaps I didn't make clear what I was suggesting. At the moment, Swindon to Cheltenham takes 1 hour and a couple of minutes. Apart from the two hourly through services from Paddington it requires 2 units to operate this service, each of which is running for barely more than 50% of the time. If the service were to split Swindon, all stations to Gloucester (50 minutes each way) and Swindon, non-stop to Cheltenham Spa (about the same), we could run the same frequency of service with the same number of units and provide a shorter and therefore more-attractive service between Swindon and Cheltenham.
So far as missing out the stop at Gloucester goes, I am only advocating this because it is possible to maintain the frequency of Swindon - Gloucester and Swindon - Cheltenham with the same stock as is used for the current combined service. However for this to be possible we would need to recast the through Paddington - Cheltenham service and probably require the double line to be reinstated from Swindon to Kemble.
My experience of Cotswold line cancellations on Monday led me to wonder whether extending the Swindon to Cheltenham non-stops to Worcester might give a faster overall journey time than the Cotswold line. I can already hear the pitchforks being sharpened and torches being lit!