FWIW, I installed (6) 16-zone Rachio v2 controllers on our property. It seems to me that if all Rachio controllers in use can have shared "Community" attributes (such as how many gallons the community used), and all of my Rachio controllers can have shared "Rachio Account" attributes, then why can't the 6 Rachio controllers on my property have shared "Location" attributes? That's all I need. In this fashion I wouldn't have to log into all 6 controllers to change, say, a weather station, or a smart climate or rain threshold. It's a real pain.
I wouldn't purchase a >16 zone controller if it was available. More but smaller controllers mean shorter wire runs, easier swap-outs in event of a controller failure, the ability to run multiple valves at the same time, and the like.
I don't need ethernet - simply install a long-range WiFi access point. It's more secure that way, and you don't have to run outdoor waterproof ethernet cable to your controllers (the cable plus installation would cost more than your AP.)
What I also need is native support for Weather Underground. I had to shut off the "smart climate" features and bump up the rain thresholds until I can kludge together a bridge to my own PWS. Don't understand Rachio's reticence around doing this.
Definitely need better fault reporting. For instance, this morning one of my Rachios got hung up at zone 5, keeping a valve powered on for 7 hours (was supposed to shut off after 6 minutes) and dumped about 7 thousand gallons of water on the zone. Kudos to customer support for swapping me out with a new unit; however something should alert me if the run time did not complete and ideally should shut off a master valve if installed.
Rachio reports on current overload. That's good. It needs to also report on undercurrents - for instance, from open wires to a problem with the valve solenoid. Otherwise it will report that zones were watered when they weren't.
I like the Rachio, especially the small footprint for outside, and the UI, once one figures it out. If you could add the above features you could make a nice dent in the commercial market.