Sounds like all good reasons to me. All of them very true!
As for the sensor being better than the lenses... Well, yes, it's a lot easier to see the difference between ok lenses and excellent lenses at 100%, but no lenses are suddenly getting worse just because you mount them on a K-3. It's just that some of them don't fully utilise the potential of the camera. So, no reason for concern. Not really. But you
will probably end up wanting to replace some lenses anyway
A grip? Personal preferences. Some like it a lot, I don't really see it helping me the way I shoot.
Good luck!