So many quotes which I unfortunately can't manage at work (old IE I think) and yes, I'm on a Tea break
In general then:
The 21 for walkabout and the focal length - agree
The 35 because it's so versatile - agree
The 40 as it's so tiny and the slightly odd(?) focal length makes you think - agree
Love the idea about the tiny(!) *200
The other option though - 21,70 as an even smaller Duo of Primes - that would work for me I think so perhaps the 21 comes out on top on this occasion.
"One last thing" to stir the pot, which is sort of on topic:
Glad the 31 came up! That's very close to the 28 (FOV of course), which I really like on APS-C, but opens up another can of worms.
Perhaps the final option is to go for the DA40 (or even FA43) to give a similar FOV in the hopes of a future FF!!