Anyway, if just one EP was going to be made, I would opt for around 8mm and 94x (S3) or 71x (S2) as being a good compromise. The 5mm EP is useful when the binoculars are well aligned, but it's really a bit too much magnification for this scope.
I don't think Harry would have any difficulty selling at least a dozen+ pairs of eyepieces in this range. Regular Miyuchi EP pairs for the S2/S3 sell for around $300-$330 and while I would not pay a large premium for EP's in this range, I would probably go up to $400 if they worked well and maybe others would too?