but what about users of the 920XT for example, barrels are not supported
Barrels should work work on 1.x devices as well; I would start a new thread if you are having issues running apps built with them on up-to-date 1.x devices.
If you don't want to work with barrels though, or just want to see how they're implemented, you can always copy out the source files packaged inside.
Barrels are not supported by all devices... the require vm support to work. All devices with ConnectIQ 2.4.x support should be fine. 1.x devices with support for 1.4.4 and later should work as well.
Travis
An overview page in the documentation of all devices (and their Apac counterparts) that shows the latest supported released Connect Iq version would be a handy thing to have (amongst others to see which device has barrel support, but this extends to all other functions in the api).
Maintaining this overview would be a bit of a maintenance hell though. Perhaps it could be a page that can automatically be generated from your build system?