yeah this makes sense, I definitely considered something similar

What made you decide against? Post button in the way?

we settled on the philosophy that the primary action should be poast. always be poasting.

so true. I might tone down the blue colour and highlight the tab button

could also work just as well reversed, just have the middle button open the menu?

I feel this would work amazingly in your design if you combined it with the trick you use for the profile preview modal 👀