I think Jade's idea about moving into the direction of xhtml and css compliance would be a major leap towards easier skinning. Like said, at the moment most packages rely heavily on tables and hard-coded design attributes which cannot be changed instance by instance. If they relied more on xhtml/css, the appearance could a lot easier be changed by using different css files in different contexts.
I don't know in which state the process of css'ifying the toolkit is, but I could for example take on the task of making lars-blogger and the parts of calendar used in blogger xhtml transitional and css compliant. Not because they would be in the most urgent need of change (at least lars-blogger), but more because I'll need them in short and as current they don't quite cut it for me.
I don't know if these kind of things need to be tipped, tho. Just a thought.
