As I am constantly telling readers of this website, there are no stratakops. However, yo do this, no one from Fair Trading is going to come along and demand that the upstairs neighbours restore the old carpet or refund money. You could push this through as a simple accounting exercise. Owners A want to replace the carpet. The OC will pay for replacement, up to a certain value, but will only do so at a flexible date in the future which will be triggered by the recarpetting of the other lift lobbies.
Upstairs neighbours recarpet and pay for it. Share of agreed recarpetting (or part of it) is recorded as a debt by the OC to the people upstairs. Two years later, rest of building is recarpetted, Upstairs neighbours’ levies are reduced by their share of total recarpetting, established earlier, because the OC effectively owes them that money.
Complicated but actually simple. Is it totally legal? Who cares? There are no StrataKops. Your only problem is if the upstairs owners sell in the interim and the new owner wants their floor recarpetted at the same time as the others.