This is what I have been calling for, the Incas have their own unique indigenous allies, you can choose a suitable one from three according to the situation of the game, Africans can ally with two indigenous allies, the United States has the Kree, Mexico can ally with two indigenous peoples, and even they can have additional indigenous troops after the revolution into the Maya, and now France and Germany also have their own indigenous allies, this mechanism is very interesting, but he actually acts on other civilizations first instead of all indigenous civilizations, This alliance with indigenous people is ripe for the other three indigenous civilizations to enjoy this power, and it should have been their first to enjoy it. I will continue to advocate for this and hope that indigenous people will be treated fairly.
Brits and their indigenous units of Scottish Highlanders. Throw in some Drummers reskinned/re-err-audio’d with bagpipes and I’ll give the Devs a kiss.
This mechanism may become the norm, but in any case it should be indigenous civilizations who get them first. The other three indigenous civilizations have waited too long, and perhaps Asian civilizations deserve this mechanism,
Drummer and Flag Bearer should be the default units in any Royal House.
The drummer is a fairly good unit, but he is better not to apply to all European civilizations, it is easy to upset the balance
Ottomans should get Tatars for sure. From a historical perspective the Crimean Khanate was protectorate of Ottomans for more than 400 years. The Crimean Tatar cavalry was always an integral part of the Ottoman army. Related to game play I don’t think it will be problematic too, it will only add a second cav archer variant. The card could be named as the “House of Giray” and could use Tengri Shrine models.
Ottos having access to Phanar, Sufis and Berbers as other choices are also accurate but could be problematic gameplay wise, making Ottos more OP. However developers could make those alliances cost a good amount of resources (like idk 300 wood 300 food age 3 card) to compensate Ottos possible access to those alliances (or adds only one unit from the mentioned civs depending on balance).
Sweden could get Vasa (without Winged Hussars for balance), in my opinion and this will also be good for game play because it will give Swedes a proper skirmisher option without requiring necessary going the merch path (Jaegers).
Cossack host should be added as a minor civ too definitely. Adding Cossack host as a minor civ makes so much sense because different Cossack hosts made alliances every major power in their region and fits perfectly to minor civ mechanic of aoe3. They can be available to, Russians, Sweden, Ottomans (also Poland in the future 
). It can have a similar mechanic like the Berben Sultan, giving access to a Cossack Hetman or Ataman who can create Cossack daredevils.
I saw a previous post on the same issue and I mostly agree about the native civs part that who should get which minor alliance so I don’t want to repeat it but don’t totally agree with the mercs part.
I hope devs will make this the norm for all civs so it will add more variety to gameplay for all civs.
How about Jesuit Allies for Spanish?
The current problem with this gameplay is that some are too strong, some are too weak, adding a skirmish to Sweden? It sounds a bit crazy. The musketeers of the second era combined with skirmishers made Sweden invincible. The Kree technology and unweakened U.S. state militias ruled treaty mode for almost an entire year, and the Incas and their indigenous allies were very powerful on some maps, as can be seen in the game, and people complained about Ethiopia and his Sudanese allies until the game was completely weakened to use. Similarly, France and Germany do not seem to benefit much from the new indigenous allies, and perhaps France has such tactics, but it does not seem to be common. Other indigenous civilizations and their allies have discussed many times that they need to be updated with a high priority, which they deserve. And it doesn’t upset the balance either. It is possible that under such an update, the new cards obtained by their test suit need to be adjusted to era three. This will be more balanced