I can’t tell you what the law is regarding this, but by way of example, some years ago a strata I am involved with had a person come around on a regular basis for general cleaning.
One owner asked the committee if instead of paying the cleaner, could he be paid to do the straight forward job instead. He offered to do it at roughly 20% cheaper than the contractor.
The committee at the time advised that in theory there is no problem paying an owner or tenant to do the work but one committee member was strongly against it in case the owner/tenant had an accident and she reasoned, the OC would be liable for compensation as opposed to a self insured contractor, where the OC would not be liable. Owners were at the time unsure if this argument had merit, but nobody was too interested in pushing for the change from contractor to owner/resident, so the matter died and the (external) person hired to clean still has the job.
In the event that you do get your way and an owner/tenant is paid per episode of “bin duty”, I think it is best that payment (whatever it is) be made directly by the strata committee to the person(s) rather than having a contra to the levies because the paying for “bin duty” is an expense of the OC and should be reflected accurately in the accounts. And for the owner/tenant that money is income.