I am a residential user (27 zones) who is currently on a discontinued Hunter ICC controller. It has four 8-zone expansion modules (32 zones) and a total expansion capacity of 48 zones. Assuming it hasn't already, possibly the Rachio Team should take a look at the expansion module concept that the ICC uses, from a design standpoint. Offering a system that comes with one 8-zone module included, but the capacity to add three or more additional modules ($), might make sense. Having everything inside of one, albeit larger, control box would also be cleaner than daisy-chaining multiple controllers; in my opinion.
Please add me to the list of residential users who pledge to purchase a Rachio when it expands to a seamless solution for systems with an above-average number of zones.