My experience is that the interior office type spaces you can usually get away with it since the minimums are so low. But the conference room high occupancy high minimum airflow spaces are the issue. You can resolve those by using minimum ventilation reset strategies which is somewhat code required anyway.

A simple exercise to communicate your issue is to see what your minimum airflow is to some example spaces and balance it against some light and a lower than normal amount of people and see what the space temp would balance out to be. Communicate this to client and see if they can live with it - and they probably have been since it’s the existing condition. I’d they can’t live with it then you have to dig into how complicated it is to connect reheat coils to the hot water already there. Is or can it be year round, what temps are available for reheat, how is it controlled and will that work for the reheat coil when you need it.

Thank you very much for the comment, it's very helpful. This is a new company moving into the building so they haven't been living with it and it's a pretty fancy remodel with lots of conference rooms. I'll do that exercise and bring it up for their decision. Thanks!

For smaller core zones, set it to a very low minimum. We have done VAV only without heat (cost saving) without significant issues. Just communicate to the owner the limitations of the system as the other poster indicated.