As you know, the Americans had indian allies during the war as well (Choctaw, Cherokee, and Muscogee) will be seeing a unit or two as a possibility to bring some balance?
Yes, you are correct but if you look at the amount of the native presence on the US side, it is dwarfed by the amount of support the British were given. That is the reason we did not include them as a unit available to the US faction. Encroachment into native lands was far more of an issue in the more populous United States than it was in British North America. Most Native tribes saw their interests as aligning with the British who also wanted to slow the westward expansion of the US. If you look at the numbers referenced on the War of 1812 Wiki
http://en.wikipedia.org/wiki/War_of_1812 the strength of British native american support was over 10,000 and only 143 Choctaw and unknown amounts of other tribes for the US. You will have to read the sources referenced on the Wiki notes to get a fuller explanation of these numbers.
Also, it is very unlikely that we will be adding further units to the mod since the size of the module is already over the size of the vanilla module and a further significant size increase risks making it unstable during game play. Additional textures required for new units take up a lot of space when compared to other things like maps.