raystuttgart
Civ4Col Modder
... native mercenaries could be "hired" by the player for a "deposit" ...
Have you ever played TAC ?
(We are based on TAC.)
Native Mercenaries are already part of TAC and our mod.

Generally:
When creating a huge mod and trying to achieve high quality, you should choose your features carefully.
Features that
A) cause a lot of changes, efforts and risks
B) add very little fun
C) are problematic for balancing
are very unlikely to make it into our mod.
"Spreading Plagues" and "Natives leading war against each other without reason" are good examples for that to my opinion.

Especially when considering that Natives are also very valuable partners in Religion and Revolution.
1. Native Mercenaries
2. Bargaining with Natives
3. Training
4. Missions
5. Various Events (DLL and Python)
...
Also you might have defensive pacts and could be drawn into conflicts all the time ...
-----------------
We could pump up this mod with endless amounts of features, but that is not what we want.

(There is a huge difference between a feature and a good feature ...)
Religion and Revolution is not about Quantity only, it is first of all about Quality.
Our main goals:
(Basically our checklist, when considering a feature.)
1. Fun
2. Stability
3. Atmosphere
4. Historical Correctness
4. Smart and Challenging AI
5. Good Balancing