I already did some thoughts on that. Removing it was necessary, as some devices wouldn't be detected otherwise. Some consoles for example do not run a mobile os.

A possible solution would be to always store the complete useragent in the visit data and detect the os/browser/device while processing the data. I don't see a reason why we need to detect those data while tracking. 
That would additionally allow us to run a "redetect" later and refresh the detected data with new definitions (which would need reprocessing all data for sure)