I had both knees replaced in 2014 after the right hip in 2013. Recovery from the hip replacement was easier than the knees (which were done simultaneously), taking about 6 months to feel "right". The knees were pretty good after 6 months and I was back to most activities then, although improvement continued for a few more months. The activities include horseback riding, cross-country skiing, hiking and motorcycle riding (first on my R100RS --- with electric start). My Vincent wasn't quite ready for the road then but I think I would not have had a problem kick starting it.
By 2016 the Vincent (D Rapide) was back on the road and I've been riding it ever since. Kick starting it hasn't been a problem; at least not for my body. In the early stages the bike was a little obstinate. The bike starts much better now. I do find it harder to start when it is stone cold and I use the D center stand for that. Once warm I start it mounted. No stand and no problem.
I might add that have short legs (28" inseam) and am 82 years, err ... old (damn). I do think I have benefited from decades of serious physical activity.
Overall, I've had a good experience with the replacements. I hope you have the same.
Gary makes some very good points on this post, and on another you have running, like Gary I also had Bilateral Total Knee Replacement on the same morning, 18/01/2022, it is so important that you use a surgeon that knows what he is doing, my surgeon used the Stryker robot assisted surgery to ensure accuracy, but once the surgery has been completed it is also vital that you start your exercise programme immediately to combat scar tissue taking hold and stiffening the joint, incredibly enough I was operated in the morning, and walking with frame in the afternoon , not for the feint of heart, but well worth the effort (and the money)
I had an electric starter fitted to my Rapide in 2018, so starting the twin was never a problem, although I did once, with much trepidation, have to use the kickstart fairly soon into my recovery due to a weak battery, but that was fine, in the early days of recovery I favoured my D Comet, but that did give me one hell of a kick back whilst leaving a West London event on the 21st May, so 4 months in, thankfully the new knee survived.
As you make the point that you are short in the leg, as I am, I think it is most unlikely that will need footrest extensions, just set the standard footrests to the lowest position, and work hard to get sufficient flexion in your replacement knee, I did all the exercises my physiotherapist set me, and then some more, I found progressively lowering the saddle on my static bike was great for achieving more flexion, sometimes it was easier to pedal backwards to start with, I have no idea why.
Given a choice I would far prefer my 20 year old knees back, but equally I would like some other parts of my 20 year old anatomy back! but we are where we are, and I am delighted with my new knees, my dilemma is my Black Shadow, a very beautiful machine, but without an electric start, and as a totally standard Shadow, I am reluctant to fit one, but neither do I want to wear out my new knee prematurely and have to go through a revision, but as my Son has demonstrated, it does start very easily, and first kick.......
Good Luck, and I hope your new knee progresses well.