System type and OA input

Hi Everyone! The project that we're working on will be in a country where the local code requires more outdoor air than 62.1 at most of the zone types. I've learned that if the proposed design has DCV (CO2 sensors) in areas beyond mandatory, the baseline would require the only minimum OA from 62.1 for those areas. Making the OA input different between baseline and proposed. This would mean in this case that adding DCV beyond mandatory will decrease the savings. That doesn't change the fact that DCV really improves the HVAC efficiency. Could we propose not to install DCV yet? Another question is for the tenant levels, the the chilled water pipe stub out s are designed for FCU. It is determened that FCU will be installed because there's no place for AHU's. For the proposed model, should we still use HVAC system same with the baseline PIU(Parallel Fan Powered Box)? or FCU? Thank you in advance!