One reason to buy maybe a suitable used set of wheels, from a lower trim level, is to end up with narrower tyres with higher sidewalls, which are both useful to have in winter time - and that usually means paying less for the same brand of tyre. As well as the summer wheels never needing to get trashed by the winter salt.
Obviously brake sizes will determine if you can drop a wheel size, or if in doubt check to see what the manufacturer recommends for winter wheels/tyre sizes.
I've always aimed to use a size that the manufacturer is happy with, as that should
help keeping the insurance happy, ie no extra loading.
I've always had concerns regarding swopping the tyres on wheels every 6 months, I suppose just in case the tyre carcase gets damaged at the rim point, and the wheels get chipped at the rim, which will accelerate the corrosion/leaking.
So far I've never ever managed to get any proper money back on winter wheels or tyres, but I've accepted that that was going to be the case, storage can be another issue, but I have a generously sized double garage, so for me that is not an issue.