There's an Issue for that on itea: #4581 (current title: Flags for all garrisonable buildings and units).

Funnily this was a topic on Reddit 16 days before OP as well:   

A couple of different possibilities inspired by that, which might need refinement to condense on one useful thing: -Target types: if one queues this with a sheep and a gazelle, the hunter would hunt all sheep and gazelles he has around. This could be also used for chopping all trees, garrisoning certain buildings, and boarding certain ships, as long as they are nearby. In case of troops, maybe it could work as cavalry targeting archers, while pikemen cavalry, and so on. -Action stances: similar as before, but the target doesn't really need to be specified. One could hunt all non-aggressive animals (or also aggressive ones if that was selected) as mentioned, but could also work with things like "repair all", "board all", etc, as long as they are nearby.

@Vrayer, congratulation on making your first mod! I have to warn you however that changes like theses will cause oos if you play with players that wouldn't have the mod. For the mod you posted, you should keep the compatibility check enabled in the mod.json to avoid problems. If you really want to create a compatible mod that does this without compatibility issues (that will not oos), you would need a different approach where the UnitAI behavior stay unmodified but triggers re-issuing a command, for other clients to serialize the same behavior as you want. That's tiny slightly more complicated to do but very feasible.

My point being that, ideally, these should be historically informed. But I wonder why this is even the case, it seems quite independent from the objective of making a bot better than Petra, which seems you have achieved and I would be interested in playing against (and I think should make it to vanilla), just I wouldn't want additional inaccurate techs (if that's the case with those, and when there seems so much to clean up already).    That's nice, although I guess it might be preferable if resource gathering speed is the same at all levels, and easier levels are easier for other reasons, to add uniformity and be easier to explain (by completely removing that "cheating" factor many don't like). Restrictions on the number of certain things seems fine to me, closer to modelling an actual player.