Talk about thread drift....
What you all seem to be missing is why offsets may complicate things. Lateral separation (not opposite direction) is based upon 1NM separation, it is always obviously larger than that, but when you factor out all the tolerances the minimum distance between two aircraft could be 1NM. Putting yourself off a track (within an airway) by 'up to 5NM' could be the last of the tolerances where you no longer have the 1NM separation...
RE talking about 'at cruising levels' at what point do you go back "on track", when descending/before gently to a waypoint, harsh turn and get back on ASAP??? Many routes in a busy terminal environment may have as little as .5NM tolerance with the minimum radar separation to the next track (ie tracks 3.5NM apart), or SID STAR cross over point where level changes occur, helping yourself to a 1NM offset (or less) is going to get the ATC a nice discussion with their manager and possibly you a please explain?
Airways still exist in some locations but in the modern world tracks are the norm. Flex tracks and User preferred etc are becoming more utilised, so this should help eliminate the constant directly on top of each other scenario, but as logic dictates what is good for one will be good for the next...
With ADS-B, ADS-C, CPDLC etc being off track causes problems, your machine is constantly updating the ATC system with 'off track advice' or non-compliance with the clearance advice.
I work in an environment where we have no tracks, yet the amount of times I see aircraft directly on top of each other is too numerous to count, each shift. Offsetting does very little IMHO to improve safety in many environments.