proportionate pools do not have the intermittent issue
That's wrong. Even setting aside the hopping issue, proportional pools have higher variance than a PPLNS pool with the default parameters. So if PPLNS is bad for intermittent miners, so is proportional.
Interesting. I see that a proportional pool (assuming no pool hoppers) proves more of a problem for random intermittent miners versus 24/7 miners than a similar PPLNS pool (regardless of the value of N) (which in turn is more problematic than most other reward systems). However, I don't have much of a feel for the value of N at which the share-based variance at PPLNS is similar to that of a proportional share. Have you calculated such a value of N or merely shown that it is less than [difficulty]/2.
Also, I completely agree. I'm not clear exactly on what the "intermittent issue" is but based only on the name I can safely say that if it's a problem for PPLNS then it's a bigger problem for proportional (certainly for N=[difficulty], arguably for all N).