Good post AC, well explained I reckon. To elaborate further on the 'can you fix a club foot' it depends on the cause - eg. If one leg is actually longer than the other, there has been an irrepairable injury or such, it may be impossible & undesirable to even try. I also think that - emphasising your point AC - if it's left solely to farriery, it may also be undesirable to even try, because it is generally a holistic type situation - you can't just 'fix' the foot without consideration & correct management of the whole horse & the underlying cause. Eg. Feeding horses from 1' or so off the ground may be the best method of 'fixing' a club foot due to grazing stance of a long legged, relatively short necked animal. Eg. Just trimming down high heels without consideration to comfort isn't likely to work well, because regardless how 'ideally' the horse may be trimmed, he's still going to land toe first on that foot due to weak heels.
I'm interested in your idea AC that the 'strong' foot tends to be more likely to have rotation though, as IME that is not the case. I wouldn't call it the strong foot either though - just low heeled - as I've definitely found that foot is also often weak, flat soled & stretched laminae/flared walls. Due to the high heel & more pressure on the toe however, I've found that while the back half of a club foot is 'concave', the front often isn't and there is also usually a fair degree of stretching of the toe. Assuming appropriate and frequent enough hoofcare though, regardless of whether or not the high foot is lowered, the stretching/flaring in both feet should be manageable/avoidable.
Back to Puck... I'd pretty much ignore butt cheek
size with regard to heel balance. I'd basically trim the heels to be well balanced in relation to the sole plane. I'd be using frog support wedges to give the frog comfortable stimulation - & ability to get stronger - on the high foot.
No you can only fix em if the horse will hold up to work and use. Permanent injuries and defects like bone spurs, ringbone, sidebone, arthritis, bowed tendons, navicular, etc. are irreversible and sadly will likely just be a pasture pet
I agree that it *may often* be impossible, in many particular circumstances, but I don't believe that's all *necessarily* irreversible, as bone remodelling/calcification responds to how the bones/joints are used. I have had personal (anecdotal, no rads, sorry) evidence of ringbone and osteoarthritic knees improving greatly & calcified areas reducing when mechanics were changed. With regard to 'navicular disease', while there is no evidence to my knowledge to suggest bone remodelling there can change back to a healthy state, there is plenty to suggest that with appropriate care, the bony changes can be irrelevant to the horse's comfort & use. ***Not at all trying to say everything is cureable in the least, or even that it is easy or even always desirable or worth the effort, just that it is not impossible IME.