Well, that only works if you're not running fullscreen... Else there's non-trivial cost to launching it. So I was thinking a persistent, always-on-top window would be best.

Oh, that attempt... Sorry to leave you in suspense; it was an utter flop. What's there is the best you're gonna get by this approach. Did you try it?

Personally, if I wanted this kinda thing, I'd be inclined to use Personal menu for regular menu stuff, and stack command-navigator full of typing shortcuts like this:

Description: Foo
Command: xte 'str Foo'