I think average units shouldn’t be promoted, but if they are units that need to be unlocked, maybe yes.
I think this type of mechanic would be better for ‘native’ type units, since it is a quality that encourages its use. The truth is that if this was not in the game now, if we had proposed it before, it would seem absurd and exaggerated, but I think that now many units could benefit from this.
For example the ‘Nootka War Chief’ could increase the speed and maybe the damage of the ‘Nootka Clubman’ with an aura bonus. I know it’s not the same as promoting, but it’s the kind of thing that would suit natives well.
The Tupi and Carib warriors could have poison damage, that is, damage as a result of the shot, just like ‘The Jungle Bowman’ of the Incas.
[Minor Natives topic] Post here your ideas for every single minor natives so the devs can look at
Catalog of proposals on minor factions/civilizations (AOE-3 BASIC + TWC + TAD)