I did something very similar. The only thing you haven't mentioned
is GFCI outlets - I had the same goal of having every box be easily
switchable from 110 to 220, but ultimately made up several strings
of GFCI-protected 110 outlets. If I change my mind, I can go
back and install more individual GFCIs and still make up a couple
of 220V outlets ... right now, my 220 stuff is on separate circuits,
My outlets are mostly about 50" above the ground (so I can store
a sheet of plywood below), with some low to the ground where I know
I want things like a fridge or vacuum plugged in. Maximum spacing is 6'.
Figure out where your fixed bench is going to be and put extra
outlets there. Plan for a nest of battery chargers, too.