How to make the native semi-civ more useful?

Other ways to improve the alliance with the natives would be:

The natives who use firearms or metallic weapons such as spears, swords or pikes would cost gold instead of wood.

If the natives with whom you are allied use firearms, but your civilization does not use firearms or have access to the arsenal, then in that town some improvements will appear associated with those that would be in an arsenal.

The capitol upgrade ‘Deforestation’ makes wood in the markets much cheaper, and the trading posts give you much more wood. Useful to be able to create natives that would continue to consist of wood if many of them cost gold.

The upgrade ‘legendary native warriors’ increases the native embassy limit by +1 and natives are created faster. (In addition to your current benefits).