Assuming that the problem here is people doing UA sniffing, the problem, like with people doing glue sniffing, is to stop people sniffing the UA (or glue) - not to make the UA (or glue) unusable for it's intended purpose.
Have you ever used a service that shows things like your active sessions, login attempts etc? Notice how they basically all show you what kind of device and usually what browser the session/login is from, with a date time and usually location?
If everyone pretends to be Chrome what's the fucking point any more? "You logged in from Chrome on Tuesday the 3rd at 8am". "Well no I fucking didn't, I guess I better go reset my damn passwords again".
Have you ever used a service that shows things like your active sessions, login attempts etc? Notice how they basically all show you what kind of device and usually what browser the session/login is from, with a date time and usually location?
If everyone pretends to be Chrome what's the fucking point any more? "You logged in from Chrome on Tuesday the 3rd at 8am". "Well no I fucking didn't, I guess I better go reset my damn passwords again".