As noted in many places over the last years, it could be a nice idea to implement some kind of ambush mechanic. So this is my attempt.
This patch gives the Gauls an "camouflaged ambush camp", which is camouflaged and not directly/ automatically targeted by the enemy (by that I mean BuildingAI, UnitAI and PetraI), but the human opponent can still see and attack it.
To make it harder for the enemy to find the camp it can be build anywhere in neutral territory (also inside a forest since it ignores obstructions). The camp is also not visible on the minimap and is not visible in the fog (minimizing the option to "scan" for the camp by hovering with the cursor).
Credits go to @wowgetoffyourcellphone from whom I got the "grove" idea, after which the camp is designed and @bb who gave some helpful tips and @Langbart who made the garrison tooltips.
Stuff to discuss: Would it make sense to not do the obstruction ignoring and just make the camp visually camouflaged insted of this "hiding in the forest thing" ?
Would it be better if no camp is used and the units camouflage directly (see 2nd video)?
Would it be better to do this with the concept of garrisonable tree grove (which belongs to gaia, as in DE)?
Here is a short video demonstrating the core mechanic: