Yes, it is confusing but I believe the breakdown of responsibility is this:
Responsibility for fence between two lots is shared by the two lot owners.
Responsibility for fence between a lot and common property is shared equally byt the lot owner and the owners corp (the other owners collectively).
Responsibility for fence between a lot or common property and public land lies with the owners corp.
Anyway, the easiest way to do this is to get a by-law passed that says you can raise the height of the fence but that you, the lot owners, will take responsibility for its upkeep.
You would need to do this anyway as you are changing the outward appearance of the strata scheme and that requires a special resolution by-law.
If the fence borders public land you may also need to get the OK of the local council.