Do you think that "structured geass" could exist? I mean a geass order is a series of simple actions stated in a complex order like "write a sign on that wall evrey day". This means:
1) check out evrey day.
2) going to the wall.
3) make the sign.
So an apparently "simple" order is quite complex in reality: could this complexity being enhanced further by making the list of the given orders longer and longer? If an order like "obey to any orders I give you" functions then the Geass is an overkill...