@datakurre nice summary of the approach. Fat themes is a nicer name than going eggless
I think you only touch on the benefit of creating quicker iterations. It's kind of hard to quantify but I can attest it makes the process of building sites more agile and more productive. You really have to try yourself to find out. I hope lots attend the TTW training at the ploneconf to see for themselves.
rapido: I wouldn't describe it as a successor to plomino, even though it was originally intended as that. It is actually more a successor to themefragments. It takes the idea of adding ZPT inside your theme and adds .py files that contain multiple python functions. These are similar view callables in pyramid. It is more pythonic than zope python scripts. In terms of using either diazo or tiles to insert it into your site, it works the same as themefragments.
If your usecase demands it, it comes with a simple field/form framework and the ability to store light records easily in a non DX/OO way. But you don't have to use that.
Is that a fair assessment @ebrehault?
c.listingviews and c.facets are the other tools we normally use in our fat themes. We find that the combination of c.faceted navigation + c.listingviews + DX often makes for quick turn around on customising search and listing pages for clients.
@datakurre have you thought anymore about the git experiment at https://github.com/collective/collective.gitresource. ie git push your theme to plone on the server, edit via the theme editor if you want and then git pull the changes back.