Nice to have a post from you, tho sad about your hip and the pain. I had a phone call from an old friend suffering too. She says she cant sit and standing is wrecking her feet. She is on pain killers all the time and would like a replacement operation but isnt yet bad enough to qualify on the UK NHS.
However, my doctor daughter feels that people we know who go private for joint replacement, take the step too soon because the surgeons etc get paid - and the results arent always perfect.
I cant advise on hips and Western saddles. And I dont know how your riding is affected by your hip. Things vary so muchg case by case. Unlike Frances who has a back problem, my own back does not respond well to simply sitting long term in the saddle. Rising trot helps me a lot. That means Western riding doesnt feel as good for me as normal UK. Tho I need an old fashioned, open, GP saddle, none of your fancy knee blocks.
My OH has sort of stopped riding -He started by learning Western and I think he might be more secure on a bouncy horse if he had learned to ride forward seat in canter. But you dont do that in a Western saddle.
I suspect that Western saddles tend to be wider as well as heavier to lift on and off the horse - neither of which helps an older rider like me.I need a narrow horse. And I think your Dolly would be too wide for me.
However, an endurance saddle might have none of these drawbacks.
On the other hand, I know from reading Isabella Bird and accounts of Bill Dorrance (Western pioneer of NH) riding in his 90s that a Western saddle gives more support and security. If my balance were to deteriorate, the open saddle in which I now ride might become too open, allowing me to slip sideways?
I have thought about this a lot because one problem of getting old and riding is that one takes more care - I posted recently that after going on a one hour hack in walk only - just to get confident on a new horse, I could barely dismount and was very stiff the next day. If your hip means you need to sit still on the horse, then it is going to increase dismounting problems perhaps?
I hope you can find a solution through RDA or a larger forum? I almost gave up riding last autumn but then was paired up beyond my dreams with my teacher's horse who has lovely tack. My share too was an RI's personal horse with her own high quality saddle and bridle. And as an RS rider I have also had the chance to ride a variety of horses in different saddles. If you have access to a yard with lots of horses maybe they could let you sit on some of their saddles?
I think it is very easy to stop riding when one gets older - We like things we are used to and feel safe with them.