homer, not quite sure I get what you mean with an NR. They certainly shouldn't get a +0.1 whatever the circumstances as this could be to their advantage. frequent NR should be penalised, though not sure how - we all work to get a cut so awarding one for failing to return? banning them from comps just means that their h'cap is frozen, which is what they are doing anyway.
the only thing I can think of that might work is stripping them of their h/cap and requiring them to requalify with a committee members signature on each card, but as we have already established that's not really going to hurt them away from home as they can get a fake and very few check at all.

as to cards, all cards issued should be returned (though I wasn't aware that an incomplete card could count toward the CSS)

as to do you finish; too right you do, medical is the only excuse.