Another model would be for the OC to own all the PV, one for common property use and four x 2KW. The OC then provides a connection from one 2KW section to each of the four units. The OC would be providing a utility service to each unit (which is assume is covered in the strata legislation in most places). Minor on-going costs would be met by the OC such as occasional cleaning or any periodic inspection that might be required by the electricity network.
Each unit could do as it pleases with the electricity so supplied: put it in a battery at the unit if they want to, or just use as much as possible when it is being made by running equipment by day, or export it through the unit’s meter for whatever tariff that unit owner can get.
BTW. In the ACT (UTMA2011 s.23), the OC can install sustainability equipment on common property with a single ordinary resolution of a general meeting so long as various matters are addressed in the proposal – a siting map or diagram, a statement of costs and benefits, how it is to be funded, and so on.