Sure, it is planed. I think it will be present in next minor version, in a week or two. Meantime please try configure you monitor. As really i spend many time to ensure it is look adequate enough on all monitors i be able to test. So most likely you have some really weird contrast settings. Maybe for a reason, so of course it must be configurable, and it will be.

Looks perfectly unnoticeable, as intended.

hotkey is impossible without embedding a script on every page, which will require access to tabs content, which i am strongly against (not only because of the security reasons, but also because this is VERY resources unfriendly, for example there is some extension which utilize this, if you will try to install them when you have several hundreds open tabs, Chrome will crash or will be unresponsive for half a hour). There some rumors that google work on some hotkeys possibilities for extensions, yet i don't know actually.

It is also impossible to add modifier key to to close tab. 

And It is impossible to hide tab bar, as far as i know.

Yet it is possible to add additional extension button to address bar. Maybe I will do this, I was already think about something like this, especially when there will be custom icons for tabs functionality, i have plans to add them from address bar also, by this button (with a menu) in addressbar line.

Yes it is easily possible, even more, i especially implement another algorithm, as this simple approach was not very usable actually, when you need open a lot of windows. But I might add an option to disable this.