Now everyone can build anything and the only difference is in quality grinding so specialization is required for rapid development.
Assigning some high end skills to relative credos could encourage interaction - trading and feel of depth in progression.
More credos could be added like architect, whitch you would need to build great hall and windmill for example, or sailor man for building knarr etc. and similar other for end game structures and items.
One would say that it encourages alts, but this already happens. And hermits would not have any serious impact since we do things at a slower pace anyway.

Lots could be said on this I think.