Seems to me we have two main categories: movement orders and behavior orders. Let's call them Movement Orders and Rules of Engagement (ROE). There are also Retreat Orders.
Movement:
Move to a point
Attack
Patrol
Stop
Rules of Engagement:
hold position vs pursue
fire at will vs hold fire vs return fire
Retreat Orders:
do or die
retreat at minimal damage
retreat at max damage
Am I missing anything?
Short answer yes.
Long answer you forgot about Guard and no Guard and The Guard State are not the same thing, just to stop people being confused here is a quick explanation of each.
The Guard State is the default behaviour of combat units, which is to say they will move to engage any units that come in to range will follow them for a short distance if they retreat but will otherwise not pursue the target more then few tiles before they leash.
Guard is a way of setting combat units to protect a structure or unit and the way that is set is by selecting a combat unit hovering over a unit or structure you wish to protect at which time the curser will change to a icon of a shied and then when you click that unit will be assigned to protect that assets and will counter attack anyone that tries attacking the assets in question.
Now while guard isn’t something I use much it is handy because I can set a couple of units to protect my trucks when they are roaming about the map building stuff and they will simply follow the truck around and protect it the same way that body guards will follow VIPs around and will protect them if they come under attack, think secret service agents protecting the prime minister / president same idea.
With regards to needed commands here is what is needed in my opinion
Primary ordersMove - self explanatory
Attack - self explanatory
Stop - cancel your current order
Secondary ordersPatrol - Move back and forth between assigned way points attack any units that are detected within the patrol area.
Circle - Circle over an assigned area of the map (VTOL only).
Guard (requires a target, either a structure or a unit)
Body guards will counter attack any aggressor that attacks there charge.
Secondary StatesPursue state - Chase the target until its dead or your units is dead, if your unit is set to do or die.
If your unit is set to retreat at medium or heavy damage then chase the target until the target is dead or your units hp drops to medium or heavy depending on which is set, at which time it should disengage and go for repair and the Pursue state should switch off automatically.
Hold state - Don’t move from your current location unless order to do so by the player, or the hold state is switched off.
Guard state (default State) - Move to attack hostile units that come in to range but do not follow them for more than a few tiles before leashing.
Fire at will - Shoot at all hostile targets.
Hold fire - Do not shoot at the enemy unless order to do by the player, or the hold fire state is switched off.
Return fire - Only fire on the enemy if fired upon first.
SugestionsThis state doesn't currently exist but would be helpful to keep none combat units out of harms way. So if a truck is out building stuff then you might want to have it set to retreat back to base if any enemy units come into range if its on its own or if it has combat units assigned as guards then retreat beyond the firing range of the aggressor while the guards deal with the situation.
Retreat upon enemy detection (new)
Again these states don’t currently exist but would be helpful to give you more fine grained control over your units especially when using specialist weapons like bunker busters the idea being to extend the existing file control states, when a unit is set to fire at will these states would determine what that units will auto fire at.
Attack units and structures (default state) (new)
Attack structures only (new)
Attack units only (new)
Now with regards to the range states I'm not really sure what they are supposed to do, i have tried them but was never able to figure out what they where supposed to do because by default units will normally attack at the maximum range of the weapon anyway since no units with the exception of artillery can fire further then they can see or at least not in campaign mode anyway so I'm not really sure that there is any advantage to be gained from restoring those unless someone can clearly show what they where for and how they work.
finally this video demonstrates the correct behaviour for guard hold and pursue, however you want to implement it
https://youtu.be/Fz_vvwFovIo