Glad to see I'm not the only one that sees titlebars as an issue
(one of the reasons I enjoy GTK - they are trying to turn those into something actually useful). Getting rid of titlebars on maximize windows is one of the first things I do on my Gnome / Cinnamon / Xfce installs.
But I get it that Budgie devs may be hesitant to the idea as they have to take a whole of the UI design goals into consideration - otherwise we could end up in working, but somewhat rag-tag , kitbash-looking interface like some of the other de-s.
I've did a quick tweak in Krita of your proposal - moved the window title and buttons to the centre, leaving all the other stuff on the main bar intact. This potentially could work better design wise - considering raven sidebar placement to the right. Also such applet could incorporate some funky horizontal roll effects when switching (alt+tab) between windows. Just a thought:
But for me even an advanced option to simply undecorate maximized windows would do the trick.
At this point, after playing with Solus on my laptop I'm leaning towards MATE version (if it won't cause problems on my main workstation - live usb behaved a tad funky) - even though I prefer uncluttered, more straightfoward design on Budgie (and overall look and feel).
With Compiz tweaks added to the mix MATE allows me to achieve better use of screen space. But would switch to Budgie in a heartbeat if I could do it there