Whether an O/C would be responsible for the proper maintenance of the entirety of works undertaken on and attached to its Common Property or only to that property as it was in its as-built form is a moot point.
Clearly the former is my view and KP has another, but I’m sure we’d agree that such matters only become issues when, as I originally suggested, an O/C becomes aware of such un-consented works and does nothing to remedy the situation.
braveheart is a member of the O/C, he’s aware of what’s occurred, and in my opinion has an obligation to act and inform and not to get involved in peripheral discussions around what may in future happen if he/she doesn’t.