The best fix would be to avoid using common css rules for common li tags in any themes and use only class or id specific rules, If some theme sets for example margin for li it effects both ul and ol list margins. And since we can't remove yui css rules like
from file lib/yui/3.2.0/build/cssbase/base-min.css (or can we - is there a way to block some yui css files in themes?)
the next trial could be to add new rules like
ul ol li
ol ul li
to base theme css to fix cases where ordered lists are inside unordered lists or unordered lists are inside ordered lists.
But once we create lists that have lists inside lists inside lists this approach fails again...