Why would there be a detriment to others if the OP buys the land and maintains it? Wouldn’t everyone benefit from the uplift in the appearance of the building? The land has no commercial value to anyone else in the building, especially in its current condition.
Maybe what you mean is that the others experience a detriment because the OC loses control over the land, and the opportunity to make it look nice. If that’s what you meant, then OP would have to fight the OC to make them do their job – and I don’t know enough about the Victorian strata laws to know what the OC’s responsibilities are in this regard.