No, I don't think so. It would work with a 32 spoke hub provided the spoke holes are centered on the rim. If you have right side holes and left side holes, you'll have some spokes going from the right flange to the left side of the rim, which may make things weird.
If he used and skipped in pairs, the spoke holes in the rim would all be angled correctly. However there will be several different spoke lengths needed.
You are right about right spokes going into left rim holes being a problem though. I made two otherwise identical 18 hole recumbent wheels. One skipping every other hole in the rim and one skipping every other pair. The one with every other hole skipped started braking spokes after one season. The other one lasted 15 years.
If I was going to use a 48h cassette hub and rim on an R20 I'd remove all the spacers from the left side and end up with plenty of dish but not have to spread the frame much, if at all. Then I'd use 36 spokes, 24 x2 on the right and 12 radial on the left.
Sammy,
If you do get the Nexus hub. there is plenty of room between spoke holes to drill a few more and end up with 12 evenly spaced holes on each side and 12 unused ones.