It is my understanding that only a right of ownership will impact the unit entitlements. A grant of exclusive use is not a right of ownership.
As for needing council approval for the proposed work …. I am pretty sure you would require council approval. You are changing the use of that space.
I personally think that your OC should not have approved your renovations to the roof area. It appears that you may be preparing to rent this space out being that you are creating a kitchen, bathroom, and an office that you are saying that you will use as a bedroom, and possibly make a profit from it. In my opinion this is not what the original grant of exclusive use would ever have envisaged.