Hey Snare,
This looks pretty good to me. I started a thread a while back asking about the same basic question but without the true-bypass switch. Induction pointed out that (as in your diagram) the unselected inputs aren't grounded which can sometimes cause oscillation problems on some effects.
I worked up an (unverified) layout for the a 4pdt switch to allow for grounding of the unselected effect loop input. Adding the true bypass should be easy, but take a look at this and see if you think it would work...
T