to be honest i don't think this conversation should be focused on what makes sense and what doesn't. For instance, i couldn't care less about the degree of "challenge" a game presents (i never play on the hardest levels of difficulty). therefore an additional difficulty level wouldn't make sense to me (i wouldn't use it anyway).......
..but of course that's just me, and it would be foolish of me to assume such an additional feature wouldn't make sense, simply because i wouldn't be interested in it.
Same goes for new game plus imo. i'd love to replay the game again, but i'm kinda put off by the idea of having to collect again all the diagrams for the gear and the potions. Therefore i'd love a "new game plus" feature (regardless of the lack of challenge of my second playthrough). But, again, that's just my personal opinion, and i can't assume everyone else should share it.
i think it all comes down to how many people would wellcome such feature. if there's enough "demand", then it would be nice if the developers would look into it and make it possible.
btw Tuco, u picked a fantastic nickname and avatar!!