I'll have to give it to you. This is a lot better than what I've come to expect from you. This highlights one of the nice things about CCBS, The parts from the core system all look like they're meant to go together, something that can't really be said about the Inika Build, or even with custom builds based on G1.
The one thing I think is off-putting about this MOC are the straight-attached katanas on her back, the way they look in comparison to her body just doesn't work out. Would suggest finding a away to attach them so that they "cross each other" across her back. I also have some nitpicking about her black feet (though I expect it has something to do with there being no new feet pieces on Tan) and her back, which would look a lot smoother if it was covered in one or two larger armor plates.
Lastly. You mentioned you wanted "twintails" of sorts for the MOC. Although I don't have that much experience in that regard, my advice for that would be, firstly, to make the "hair" a different color than the rest of her body. The way the Pohatu mask is designed might mean that silver hair would fit well. Secondly, try to find pieces that resemble the way hair, a ponytail in this instance, would look. Tubes can be a good start.
Looking forward to seeing more like this in the future!