You don't need to be too anxious about stopping down a lot.
Though it is true, that diffraction starts to kick in at some F-Stop,
it is relatively benign to sharpening in post.
I made some landscape shots with my Fuji X-E2:
16 Megapixels, Pixel Pitch 4,82µ
According to this Wikipedia
Article the Gaussian approximation to the Airy disk is about one-third the Airy disk radius, i.e. 0.42*wavelength*F-Stop.
Since visible light is somewhere between 400 and 700 nm wavelength
at F22 the Gaussian approximation lies somewhere between
0.42*400*22 = 3696 nm ≈ 3.70µ
and 0.42*700*22 nm = 6468 nm ≈ 6.47µ
For my sensors pixel pitch this means I will start with a sharpening radius between
and 6.47µ/4,82µ≈1,3 pixels
which ends up in a
rule of thumbs of starting with about 1/15th to 1/30th of my F-Stop in pixels for the initial sharpening radius to eliminate diffraction on my specific sensor.
Since focus blur and other effects also come into play the radius might differ, but you get something to start with.
Hope thats not too far off, just wanted to take away the fear from the diffraction monsters lands beyond F8 ....