I have experience of installers’ advice about what is feasible and have learned to be sceptical. Their advice is frequently just what is quickest and easiest for them or even just what they usually do. Some have very little imagination for creative solutions. With a little push, it often turns out that what is wanted can be done. Have other units managed to install RCAC with the compressor in the rear of the units and not at the front? If so, it can be done. Perhaps the two units with compressors at the front were unilateral action by the two owners and not approved?
Where I am, people often want to put the compressors in a location on common property that detracts from the appearance of the site but puts the compressor out of the unit courtyards where the owner would see it and where its effect on appearance would be much lessened. The common property location would be consistent with the usual style of installation that installers are accustomed to so that is what installers recommend. As a committee, we are forever telling people to go back to the installer and tell them that they can do it differently as proven by various approved installations that are kept within the unit areas.
In my particular unit, it would not have been possible to put the compressor outside the unit area unlike most of our other units. Regardless of approvals, we had no choice but to do it within the unit area. It was also not possible to put the plumbing over the ceiling for the usual high wall units due to a second floor. Instead we have one larger compressor in our courtyard for a multi-split system that can run any combination of our multiple internal units mounted low on the walls of rooms. The plumbing for the refrigerant fluid and drain lines go under our suspended timber floor. The low wall location is better in any case since we use the system primarily for heating.