Thanks for the comments. I certainly understand the "officially supported" options. IMO, the bizarre limitations around device compatibility is going to keep the "smart home" space fragmented, and with the exception of tinkerers, it's just not going to hit critical mass anytime soon.
I want that Kwikset 916 touchscreen for my front door, and even though Comcast and Kwikset have a working relationship, they apparently are only agreeing on on the 914 as a supported device. Otherwise, every Kwikset lock uses a competing technology (Z-Wave) which the Comcast Xfinity Home system doesn't even see. What a mess.
Glad to know I wasn't the only person exploring beyond the devices with the official stamp of approval. It's a shame we couldn't get it to work.