Three thoughts (with a lot of maybes in them):
Is the unit effectively being treated as a short-term let as opposed to a series of problematic, but longer-term tenancies? If it’s short-term letting, does that give the OC some means of dealing with it via By-Laws?
When the residents are there as part of an agency’s help program, that might mean that the lease is not a genuine residential tenancy. It’s possible that an accommodation assistance program might actually require a Development Application to Council, in turn requiring community consultation before approval (eg one I know of for recovering drug offenders – it was rejected). However be aware that most Councils are pretty sympathetic to such programs.
Lastly, if the Lot Owner is not interested, perhaps an approach to the organisation concerned might help. While they usually make sure that the lease is in the resident’s name, they do have some duty of care to inspect the dwelling and to meet with their clients. If the OC has documented complaints about behaviour and damage, that might prompt (and help) the provider agency to take more interest – at least in vetting the clients who end up there.