I think that if Paul was a young songwriter today, he would more likely be performing honest rough-edged rock songs like Kurt Cobain, rather than some hack writing goofball crudola for Westlife / Backstreet Boys. We all know when Paul was a youth in the early days of The Beatles, they were as rough as they come...the Hamburg lifestyle was probably the same kind of sweaty violent experience as a Nirvana gig in Aberdeen.
Also like Kurt, Paul had a soft / artsy side which elevated him above the madding crowd, and both people could write tender songs as well as they could pull out awesome rock riffery and amazing chord progressions. I think McCartney, Cobain and Dave Grohl would all be great friends if they were all the same age.
Pete Townshend is another legendary rocker who was fascinated by Kurt Cobain, and was a huge fan. The chilling thing is, Pete knew about Kurt's illness situation and tried desperately to meet him in the days leading up to Kurt's suicide. Apparently Pete's calls were ignored / deflected by management / handlers each time, unbeknowst to Kurt. Pete thinks he could have done something if he was able to reach him in time, having experienced some of the same things, and dealing with the notion of being a celebrity and the cult of personality which surrounds it.