Just to make this quite clear: there has, as yet, been no firm conscious decision to exclude the Ruler from the army. Extra code is needed to accommodate the fact that the Ruler has no liege, and may have no estate. It hasn't been written yet.
Tom has made some noise, in the past, about preventing the Ruler from taking orders from someone else in the realm. However, this current situation is not a consequence of that, but rather a natural consequence of some of the New Estate System changes.
