Under the assumption that the above proposal would work, there will be the need to change the unit's appearance to help the human player (think of continuing a saved game). Typically, you'd expect the Ranger to be invisible. If it's not, you should be enabled to see this by the unit's appearance to avoid exposing it to the enemy's counter action. Which in turn means the need to change unit display depending on the state of iIsInvisible. I'd guess that one could copy the code from naval units for this (as they change their appearance when damaged). Nevertheless, you'd need another image to be displayed.