I am curious as to what your HOA decided. I am not surprised that he would be against it since he has an interest in the other company. When I first started using open sprinkler I showed some reps from Hydroscape/Siteone, Rainbird and couple of large landscape firms which I will not name and they were all just amazed at how advanced this little micro controller was and just not limited to irrigation. For us. here it has just made a lot of sense. We are now at 22 installed with almost 50 cameras.
As for the master valve scenario we tried that long ago. We mainly water during the night. I have found there to be more maintenance when you release the pressure than the opposite. Especially on 1.5″ to 2″ lines. Not to mention seepage when you turn them on and off. I have 2″ Irrigation mains with backflows. From here I have about 40-50 2″ valves behind that. My property is sloped and also has a lot of hills which also syphon water when not pressurized. I do use check valves on many of them but the syphoning takes its toll on the diaphragms.
Lastly, since I have staff on during the day, when the system remains charged, leaks are easier to detect.