User agent is one of the big players in fingerprinting. Ideally it should be entirely removed, perhaps replaced with something related to the type of device (computer/tablet/etc. assuming is needed) rather than all those details about bowrser and OS that shouldn't by anybody's business.
If websites need to detect particular features they can certainly do with JS, they do not need to know I'm running Linux on a 64 bit cpu with whatever 'point' release of the browser.
At home I run an agent spoofer extension on FF that rotates UA strings (just because i feel like), but given the sadly low user base of FF they should do it by default.
A bunch of the fingerprinting properties can be automatically tweaked 'just enough' by the browser and you will always appear unique while not losing any functionality.