While I do have Wayland in mind, that's specifically for what I can do with the GTK+ backend when running against GTK+'s limits. For this particular feature, there's a different rationale, but I can't remember what it was right now. That being said, I may add such a thing in the future (there's something in futureplans.md about centering the window right now, so...).

And yes, this is still rather incomplete (I'm surprised it's getting so much attention this early!); please feel free to make suggestions!