So, my question is: is it possible for somebody who's just in the middle of reading yaht.pdf to implement such things, or it's too complex and migration should be postponed for now? Some, but not others. Your xkb mod would not be a good one to start with, though it sounds pretty cool. My first contrib was SwapWorkspaces, which is ridiculously simple.
Your gimme.jl is a slight mod of my, I think, third contrib, WindowBringer (which arossato ported to WindowPrompt, or XMonad.Prompt.Window if you're on darcs). It'd probably be feasible to figure out how to extend either, as appropriate. So, it depends on where you are. For me, it took me from programming Haskell in the small (in ghci, pretty much :) to programming Haskell in the medium. Devin