I applaud the attempt at something different, but multiclassing and archetypes are not the same thing. They may look similar, the difference is thematic as much as mechanical.
Archetypes should work with multiclassing, thats what makes PF1 work so well, but don't start limiting one or the other.
I just want the playtest book to get here already, I'm tired of the mixed reaction I'm having to these blogs.