I agree in the basic idea. Devs should aim for a system that satisfies elite raiders, "new-to-nim-proggers" and wannabes like me .
As a huge civ fan I remember that devs made only-awarding-boni for civ5. I liked that positive approach a lot, bc everyone comes out with some positive feeling. Imho, they should not remove loot, chievos lockouts with removing stacks. They should instead add extra chievos and maybe a 100% drop of mounts (EC/TFB/S&V) and/or extra titles for ppl who clear it without stacks. But pls no surviving chievos
However, they should remove stacks from hm as well and adjust spike damage a bit in nim mode while not having stacks.
Edit:
Probably just add another level above nightmare. It's easy to copy/paste the code and do new chievos for it and easy to adjust mounts etc... :-)