I think the main issue is barrier to entry. I've worked on OSS in the past, but Android is almost completely foreign to me. I wouldn't have a clue on where to start fixing this issue.
Do you think I know? I don't have any experience with this area, yet I work on all of these issues when I can reproduce them locally. I can't do that with issues limited to specific carriers not even available in this country. Research is part of the work. Android is far too broad for me to have lots of experience with the areas that I'm working on. For example, I just had to work on the Bluetooth implementation, and I've never touched that.
The fact that Android builds take forever doesn't help either. Right now, it seems like any change I make requires 3+ hours of building, as I don't have access to a server that could accelerate builds with 64+ cores. Even then, it's a 1 hour feedback cycle.
It takes ~100 minutes on a quad core for the initial build and then incrementals builds are only a few minutes, as long as you're using an unlocked device to flash images via fastboot and not signing the build. Most changes can be done with incremental builds, and many of those changes don't force much rebuilding.
Have you thought of expanding COS to developers who would work on it as a (perhaps part-time) job?
Who would we hire when no one has demonstrated a willingness to do serious, productive work? We can't afford to pay people that aren't going to be productive.
Have you looked for investors?
No, that would destroy the purpose of this by losing control over it.