IMO FirefoxOS wasn't well received partly because it wasn't Android-based. Ultimately I wouldn't try to do a mobile OS without ~$10B in marketing/ecosystem funding.
Agreed, it needs to be Android based - the other option would be to implement iOS APIs, but Android would be a lot easier.
An analogy would be if you make a browser, to use standard HTML and HTTP, not try to invent your own thing.
Its fork, KaiOS, is widely successful (but Proprietary). They should have stuck with it.
I'd love to see this too. Would love it if it was an OS that scaled well from desktop to mobile (at least tablet) sizes. I'm a big fan of the basic idea behind Chrome OS. Not so much a fan of giving Google my info. Would be nice to have a real alternative in this niche.