I'm 67, I weighed 160 kg, (over 25 stone) in February 2022, I've lost 67 kg (10.5 stone?) since then.
Last year I noticed flaps of skin hanging from my deflated forearms, like the wrinkled arms of a bedridden geriatric. I couldn't be sure if that's what happens to your arms once you turn 66, or if it was due to weight loss, but I am happy to report that the flaps have all but vanished again now.
My massive double chin got absorbed, and left dangly wattles behind, but they have already shrunk quite a bit.
The padding on my face has been depleted, leaving me with eye bags and jowls. It's too early to tell if this is temporary, or if I'm going to be one of those old ladies who looks like a bloodhound.
A few days ago I noticed that when I stand up and lean forward the skin on my thighs wrinkles above my knees, in a way that makes me think of elephants. So then I checked my elbows with my arms straight and bent backwards, and I have elephant knees on my elbows too.
I don't care a fig. I've finally, after more than two years, hit the target of mere obesity, after being morbidly obese for decades. I can fit into a size 18, I was wearing size 36 trousers before I started following advice heard on the Zoe podcasts. Originally in the hope of reducing my levels of chronic inflammation and being able to walk without pain. The weight loss was completely unexpected, as were all the other health improvements.
My blood pressure is now down from 150/88 to 112/65, my blood glucose is within normal range 98% of the time, and for some unknown reason I now get sleepy in the evenings, after being unable to get fall asleep before sunrise since the early 90's.
So in answer to your question, yes 6 stone is doable, and at your age I'd expect the skin to readjust to your new body size. Perhaps you won't be beach body ready a couple of months after hitting your target, but by the next summer I bet nobody would be able to tell.
Personally I'd never dig into my meager savings to pay someone to knock me out and flay me alive while I was unconscious, I'd rather have elephant knees and bloodhound jowls and save the cash for fun stuff (like replacing broken down appliances). Some people love plastic surgery though, so your mileage may vary.