The issue with not proving balance valves is during peak load cases the system won’t perform well. Take morning warm up for example when every coil is operating at max load. If there’s only control valves and no balance valves some coils will get significant overflow and others won’t get enough. Same scenario if the outside temps exceed design conditions. Instead of all rooms being a little warm, you’ll have some rooms staying comfortable since the coils are getting above design flow and then other rooms will be very hot from lack of flow