Hot Water Temperature Control

I am proposing to renovate the bathrooms of a recently purchased strata unit.

The water pressure varies from room to room and in some cases the cold water pressure is greater than the hot water pressure making it difficult to safely have a shower.

The cold water is supplied under mains pressure and it appears that the communal hot water system is either gravity fed or under a lower pressure.

I do not have direct access to the HWS which I believe is on the roof of the building. My contractor has suggested that a plumber will need to access the HWS and modify it to balance the water pressures.

In July 2013 Fair Trading issued “Plumbing Industry Technical note 1/2013 regarding new  installation requirements of temperature control devices.
The note states that when replacing all fixtures within an existing bathroom and the existing heated water supply has no temperature control device installed a temperature control device is required. Only the replaced ablution points installed are required to be tempered but the whole system may be tempered.

I intend to notify the managing agents and the residents and apologise in advance for any inconvenience.

Is the Owner’s Corporation obliged to carry out the work necessary to comply with the advice from Fair Trading?

Should the OC only be required to temper the supply to my unit or should it modify all 14 units?