Late 1990s Mavic Cosmic Expert hub
 

A few questions about a 20-hole Cosmic Expert hub:

1. Would a 40-hole rim, such as the Velocity Deep V, which is readily available at Yellow Jersey, work as well as a 20-hole rim, which is not readily available anywhere?
2. I'm assuming that the one I'm interested in is 9 and 10-speed compatible, though that hasn't been fully established yet. If so, would anyone know if a Mavic ED10 Campy-compatible freehub body would fit on the Cosmic Expert freehub? The goal would be to update the freehub so that a modern-day 9-speed cassette would fit on it nicely. Or would that not be an issue with the 10-year-old freehub body?

Thanks,
R

Depends on how it's drilled. The deep V (I believe) is drilled at an angle to allow the spokes to line up nicely against their respective hub flanges.
If you try to run every 2nd spoke hole you'd get a spoke aligned for the left flange going to the right flange, with a bit of a bend as it exits the nipple. Can't say whether it'll be critical though.

Rumour has it that Velocity can do custom drillings, you might want to look into that.

For the sake of reference, now that I actually have the Cosmic Expert freehub in my possession I can state unequivocally that the Mavic freehub body cited above is not compatible with the aforementioned freehub.