Damn, initially I thought I’d be able to answer to each one of you individualy, but it looks like this is going to be impossible to do
I’ll try to respond to a few broad concerns instead.
Ideas for improvement
Not sure if it seems like it, but we do take all of these into consideration. As I mentioned before, nothing is written in stone. We will play around with this, and let users play around with it as well. Although an on/off toggle is probably not going to happen, that doesn’t mean we’re not considering all kinds of alternative options (like the ones you mentioned for hiding it while scrolling, having a dedicated space for it, etc).
Android design standards
Now you’re just asking for a flame war Being an android engineer for several years now, you will be very hard-pressed to find someone more opinionated than me about this matter! Having said that, you need to keep in mind that those are just guidelines, and they give designers and developers quite a bit of freedom with regards to how an app should look. Designers/developers are free to deviate as much as they want, as long as they can provide a nice, consistent experience. Additionally, these guidelines change over time. Case in point, bottom navigation: https://material.io/guidelines/components/bottom-navigation.html
I’ll have to dodge this, and let @vuokko answer it She’s out right now, but should be able to respond tomorrow if that’s ok!