Ok, I think you need to research the purpose and sense of the KPA. The way you describe your concerns in regards to either selling your guitars or amps and having to rematch the sound to a new component will be the same with the Axe or with any other amp or guitar you...there's always a change...and that's why you can tweak the profile to match it but you don't re-profile the amp because of a changed component. That would be like tearing down the house every time you get a new piec of furniture. Try to understand that the profiles you get are based on your skills and taste. These might change and yes, you might not have the amp again to re-do it but unless you keep all your amps, there's nothing that can be done about it. Neither Axe, Pod, or Elevenrack will prevent that.
Except that I'm fairly sure that I am clear on the differences. Correct me if I'm wrong here, but Axe creates a more generic "overall" amp model that sounds pretty close to the original amp, if not 100%. That model includes all of the original tone shaping tools (EQ, gain, etc). The Kemper takes a snapshot of the actual sound coming from the amp, including settings, guitar, pickups being used, etc, then perfectly replicates it. Then (note that I'm going by what I've read, from both those for Kemper, AND those for Axe), because the Kemper takes a "snapshot" in time, once you start tweaking it from the profile, it stops sounding accurate. Not bad, just not entirely like what the amp sounds like when you make the same adjustments. For example, start changing the EQ curve and it starts not sounding accurate anymore. Use a different guitar with different pickups and it doesn't sound like that guitar, pickups, etc, would sound through that amp. That's less of an issue with the Axe because it's more of a generic model in the first place.
If this understanding isn't accurate, please correct me. But there are several pages here and a bunch over on the Axe forum that say the same thing, again from proponents AND detractors of the Kemper. And, FWIW, that's not a bad thing. But it leads me to believe that it would be better (or, rather, ideal) to re-profile rather than make adjustments over time.