The use of the word layer is very clearly intended to imply its one component of many.

Like if you crotchet your own steering wheel cover then is the car just a layer in your amazing unique transportation device?

I'm saying, both basically and extensively, that if you're using Chromium as your engine, you don't get to then turn around and tell that your product is a solution to a corporate world and you're the alternative of evil Google, or whatever the basic spiel of all this endless ad posts here.
Building an engine is complicated, forking and continuing Google product is more complicated, I get it. Chromium-based products can be good, and I bet most of them are better than Chrome (but then again, hitting your pinky toe at night when you go to pee is also better than Chrome, so low bar). But "the alternative to Google tyranny" they aren't. You need to at least fork the engine, support it independently, and substantially alter it, even to be considered one.
So again. My solution as a browser builder is to ask "how much money I have, and how much people I employ", and additionally, what's my actual point of doing it, what am I trying to achieve.

You forgot

4. Harang people on the internet for talking about it.

Microsoft (for example) will take over

If that happen, they fail dramatically, because they already demonstrated how good are they at making a browser, so good they threw away everything the second chromium got on their horizon. And since maintaining other people's convoluted bullshit is more complicated than your own, their chances will be even lower.