two pedals - one enclosure. How to have one switch, switch between the two?

[lethargytartare]

The advantage of this route is that you can change the wiring of just the switches to change it over to two independent stomps.  So doing the switching above doesn't limit your future options at all.

But this is yet another reason to think about loopers.  You can build a basic looper that will give you an on/off for each pedal, and an overall bypass.  Then you can also build those two pedals separately, and you're not stuck with both if you come to dislike one or the other...now, that increases your construction work a lot, but it gives you the most options.  And a A/B/Y pedal is incredibly useful!