I anticipate a no from upstairs upon submission.
Not all browsers/users will have the unity plugin installed, it’s not standard yet is it?
That violates:
Extensions may not require a third-party download to work for viewers. (Additional required software for the broadcaster is acceptable.)
Further more, a unity based game in an extension, could lead to being very browser heavy and lagging the video/chat as a whole which could degrade the whole twitch experience?
Right now, there wouldn’t be a way to submit the source for review (citing: notes about webpack and minification/uglicitication from other posts).
The current expectation is everything is going to be HTML/javascript