You don’t restrict your civ, opening with a Drush is very common, almost in every game you need to do it.
It’s still a lot. Consider the jaguar warrior, that have a +10 bonus damage vs infantry. You would give a comparable bonus to a cheaper unit that can be spammed from the barracks.
Like, just a +1 in feudal would make your militias kill an enemy one with 2 less hits, which is huge.
Minus 10% good can be balanced, if you think of every possible outcome and intervene if necessary.
Consider that magyars do it with just -15% on just the scout line, saving on militias, scouts, and spears skirms can be a good bonus. Then after testing it you can consider to buff it or nerf it.
Consider that, when browsing new possible Civ bonus, just giving a civ free sanctity and fervor is considered a very strong bonus.
Aztecs have a crezy monk rush, true, but that is mainly to compensate for their lackluster tech tree (they lack cav, halbs, gunpowder and even their arbs lack 2 important techs).
You civs instead have good barracks, stable and ranges overall, so super good monks aren’t really justified.
Also, what is the game plan for such civ on arabia? They start with a Drush, and that is good since they always win against another drush, then you can go scouts, but you aren’t on the level of magyars… and then what?
You go for a castle? For knights? You don’t have an eco lead or any substantial buff to your military, how do you keep your initial advantage?
You need to go for your UU, which is crazy good, but you will need at least a castle, and it takes time to get there. Then you need to mass them (whiis fairly easy) and hope that in the meantime your enemy hasn’t go for imp and is trebbing you down.
This civ in my opinion lack of a clear plan on what it should do good. What would be their meta? Are them a rush civ? A boom civ?
I too have made a fan design of a civ, look at how I made my 2 fan design for comparison, and you’ll see how I try to think ahead on how the civ metà will be: