In case anybody finds this interesting:
I wrote a terminal emulator because I wanted a dead-simple, fullscreen, semi-transparent window a la Guake, and I realized I could implement it in like ~200 lines of Python using libvte.
I also prefer using tmux with a simple Ctrl modifier (i.e. just Ctrl+N rather than Ctrl+B then N for "next-window"), so while I was at it, I added a "tmux mode" to bind normally-impossible keyboard shortcuts like Ctrl+[ that don't work with normal terminal emulators.
Thought I'd share this here in case anybody else appreciates shortening the prefix to a simple Ctrl modifier.