I get what you’re saying.
I think there are a few companies / products that are already somewhat “like” what you describe – i.e., a hubless system; even if they are not called that.
Consider the LIFX wifi enabled lightbulb (http://lifx.co/). It (or any number around your home) are connected by wifi and controlled by … smartphone or iPad / Android tablet. In other words… in this sub-ecosystem (just light bulbs…), this is exactly what you describe.
And, amazing coincidence (? – happens to me all the time), I received in my inbox this morning my weekly newsletter from Indiegogo and, lo and behold, there is a Project (bRight Switch) there which is closer (?) to what you describe, … you tell me, is it close? It is IP, Bluetooth, and Z-Wave too (ZigBee not mentioned).
But these are $90 each (as a funder reward) and are meant to be one per room as a camera/music/controller.
bRight Switch uses an Android powered, capacitive touch display married to high voltage control electronics and is patent pending in several areas.
Electrical Switch Features
Learning mode: Learns from your usage patterns over time and automatically turns on your lights based on your living patterns, saving you time and energy.
Dimmer: Use the kind of bulb you want. Selectable for incandescent, CFL, LED bulbs.
Wake up alarm, vacation and on-time timers: No more searching for that vacation timer for the lamp or trying to remember if you turned off the bathroom fan.
Proximity detection/motion sensing: Can turn off your lights when you leave the room, or when no one is using it—great for safety and saving energy.
Z-Wave control: On/Off and dimmer functions.
Temperature: F or C display.
Nightlight/daylight: Dims/brightens screen automatically
Other features: Clock/date display, room name/message display.
Voltage / Frequency: 110-240 VAC, 50/60Hz, 600 watts.
Arm One or All: Selectable between arming one unit or all units.
Video: Live or recorded video.
Video Transmit: From switch to switch. (Wi-Fi Required).
Proximity/motion Record: Records video of the room when alarm is set.
Sends Message and Image to Phone: When alarm is triggered.
Video Block: Camera Cover blocks/un-blocks video and images.
WiFi Camera: Accepts WiFi camera video for baby’s room, front porch, or?
Bluetooth Camera: Accepts Bluetooth camera video. Blue Only.
Zone Arming: Future feature-coming.
Sends video to phone: Future feature-coming.
All Call: One unit calls all units, then listens.
Room Talk (Call): One unit talks to one unit.
Room Monitor: Great for listening for baby.
Bluetooth headset: Blue only.
Phone Follow Me: Future feature-coming.
Follow Me Automatic: Future Feature-Music follows automatically. Blue Only, must carry Bluetooth device.
External Bluetooth Speakers: Blue only.
Follow Me: Music forwarded unit to unit. Must select at each unit.
Follow Me Automatic: Music follows automatically. Blue Only, must carry Bluetooth device.
Runs Standard Android Apps.
In other words: Are you less baffled now? … Do you think the market is stumbling upon the cost effective / elegant solution you are thinking of? What will it take to eliminate the “hub” system: elimination of home ZigBee and Z-Wave? Are there non-efficiencies reasons that a company (like SmartThings) would PREFER to stay in a hub-cloud-mesh ecosystem (i.e., is it more profitable due to lock in? If the controller is simply a wall mounted iPad/Android and all Things are connected by standard wifi and/or bluetooth, then customer lock-in is much more difficult, since switching to a competitor can be done by just picking a different App to install on the tablet???