Would there be scope for a proposal for some shared common facility on that area that might make people perk up? Perhaps a shared BBQ and paving with some picnic tables?
Alternatively, the area could be granted to the ground floor unit owners with an increase in their unit entitlements and a consequent reduction in everyone else’s. That would mean they pay more levies and the rest pay less, though they would have greater voting rights too in a ‘poll vote’, assuming things work like that in WA.
If it were given away for nothing, a condition of the grant could be that the area be kept in good order with the OC retaining the right to require changes to the landscaping.
You would need to know what type of vote is required if the grant is formalised. In some states it is a special resolution but in the ACT an unopposed resolution is required to grant a ‘special privilege’ over common property. An alternative, if people agree, would be a less formal arrangement in which the OC resolves to allow furniture, gardening etc by the ground floor units on that area of common property subject to conditions including that those permissions can be revoked. All unit owners retain their right to use and enjoy the area, even if they would not in practice, and these permissions are not to be taken to be a grant of exclusive use. IE you might be able to find a way that allows it while still being reversible.
As for the balconies, reassure the unit owners that nobody has the right to enter their unit and nobody is likely to get up on their balcony with a ladder!