If I worked in the sprinkler market, here's what I'd do to address 1.8M gallon usage, $40,000 water bills, etc. This suggestion requires no changes to Rachio's units and is implementable immediately.
Rachio clearly says it wants to be a s/w company. Thus, don't wait to proceed until you can get h/w enhancements from Rachio (LCD screen face, other things mentioned above, etc.) There's no reason to not proceed now.
I work in energy monitoring and reduction areas. For our real time energy monitoring, we use a 'black box' approach exactly as Rachio does. The 'black box' has connected wires, it does processing, and it needs an Internet connection to function properly.
Most of the time we connect our 'black box' to the customer's Internet connection. But sometimes, the customer won't allow for this, or there isn't an Internet connection available. In this case we use a Wi-Fi to/from cellular communications 'box.' Work fabulously well.
We use CradlePoint's COR IBR600 Series units - https://cradlepoint.com/products/cor-ibr600-series . We don't bother with external antennas - performance in metropolitan cities where you have Verizon, AT&T, Sprint, T-Mobile, etc. is excellent.
We buy our units through distribution so I don't know cost on retail market. I looked on Amazon - https://www.amazon.com/CradlePoint-COR-IBR600LE-VZ-Router-Verizon/dp/B00BCLCSJW - $645. A bargain for HOAs and commercial properties and areas where there's acres and acres to be watered.
Slip in a SIM card, spend 5 minutes configuring the WiFi to 'talk' to the Rachio Iro, and you too are now in the business of running a sprinkler controller network without any wires. And it's doable this moment - no need to wait for anyone to go cut that 1.8M gallons, or that $40K bill.
Put the Rachio in 'automatic' mode (flex daily), configure the Rachio, and 'let 'er rip.'
You will run up on two problems, not unexpectedly:
You'll have zones where flowers are planted simultaneously in the same zones as trees, shrubs, etc. You'll have to go add valves, etc. to create more zones to avoid over watering the trees/shrubs or underwatering the flowers. (This isn't a limitation of Rachio - it's a fundamental rule of correct sprinkler system design.)
You may end up needing more that 16 zone controllers (i.e. see above) or encountering more than 16 zone controllers. As has been said numerous times here this is a limitation of Rachio controllers (currently).
There's no reason to not get on with these 1.8M gallon / $40K situation. Rachio in automated mode will probably save a lot of water.