I tried the 'use-them-indians-as-punching-bags' tactic with mixwd results. First i pick a tribe i don't particularly need (wrong specialist trainers), then i bleed them dry with trading, and, when i have a bunch of soldiers, i declare war and attack them, but leave the settlements unmolested. Usually they will start to churn out more and more 'brave-warriors' which give (some) exp to my vanilla dragoons, thus, i start to muster not only greenhorns, but also some upgraded dragoons. Downside: any bandit out of my control will make mayhem with my tile improvements, like farms, roads etc. And, as long they as sit tight on one of my tiles, that tile is useless to me. Plus, i will inevitably suffer losses, so, any soldier lost in my indian war is one soldier less i can use to fight the dreadded REF.
The developer made some confusing choices, like naming the various types of units. For example, a howitzer IS a piece of artillery. A cannon IS a piece of artillery. "Artillery' is NOT the name of a certain weapon, but a name for a family of weapons. In CivCol that leads to confusion. Everything that spits cannonbals should be named 'artillery'. Maybe they could have named the King's artillery pieces '8-pounders' or 'howitzers' or something, but NOT just 'Artillery'.
