Download ERM Script editor and edit Skeleton stats way you want them. I don't know is it possible to add new but if you change example some lv10 Dragons animations/icons to skeletons you cold have boss skeleton whit stats and specials you want. Easiest way is to change Skeleton Warriors to strong creatures and then possible ban them from Necropolis towns if any.
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Don't be too proud of this technological terror you've constructed. The ability to destroy a planet is insignificant next to the power of the Force.