Can you provide an example of what you're trying to accomplish? I don't think you can use variables in a skin rule - but perhaps you could leverage the newer skin inheritance feature to accomplish what you're looking for?
Also, in general, I find the most successful PSC posts are those that pose a specific question, and in that regards this one is pretty open ended. You seem to imply that Pega's skin rules are not maintainable, or consistent? Without knowing more details about your specific scenario it's really rather hard to comment on that.