So briefly (for C&S mechanically ventilated spaces):

For densly occupied spaces we need: CO2 monitors and i.e. air flow monitoring located in the outdoor intakes of each central HVAC

For non-densly occupied spaces we need: i.e. air flow monitoring located in the outdoor intakes of each central HVAC (without any CO2 monitors)

For tenant spaces : we can (but don`t have to) include future expansion for CO2 monitors.

That is the simplest solution, but I`m not sure if I`m right?