[Edi]

The problem with province based movement and queueing movement commands is that if an event happens in a province so that its ownership changes (barbarians, vinemen etc) or someone else conquers it, all commanders and their units which would move thorugh that province would have to have their movement orders reset, especially if their strategic move would allow them to normally bypass that province instead of having it as the destination of a turn.

I suspect coding the path determination algorithm would not be trivial since you also need to account for terrain, strat move of units in the army etc.

Games like Heroes of Might and Magic, Age of Wonders etc had it different, since the movement system is different and blocked paths are easier to check with fairly simple algorithms. You could do similar shifting path algorithms as those games, but this is something that Johan K would need to do and I suspect it falls into the category of "not interesting". That means its likelihood of being implemented is low. As I recall, vectoring has been asked for in the past with no result.