Establish military districts, particularly in France (even England has to worry about the rare invasion or the Scots.) More districts is better, assuming good men can be found to accept responsibility for them. As always, there will be need for good field commanders within these, and logistics and scouting support. The more that logistics can be delegated, the less the burden will be on the crown, and hopefully, the quicker we can move on the crown's behalf should need arise. The chain of command should have as few links as possible, however, as too many will tend to promote delays. Perhaps the Connetable or a Marshall should be appointed for any activities needed outside the crown's demesne and given authority as needed to call upon resources within the military districts. This might work best as an as needed appointment.