Any chance TG would be willing to support submitting stream videos from Mixer? Videos of the streams are available on the site, and downloading is supported.

At least for recording on the Xbox One, the saved Mixer streams are higher quality.

As a sample, here's one of mine recently streamed...

https://mixer.com/GibGirl?vod=13000229

The URL I see from the download link I have is
https://vodcontent-3002.xboxlive.com/xuid-2759124950299278-public/f76fd14f-04ad-4989-b1cc-61029ceb2205/source.mp4