I do like the idea of scalable difficulty, quite a bit. (For what it's worth, in Toto-rak you can already decide which path you're interested in taking and how difficult the instance will be as a result, and it works fairly well, so I think the devs are already thinking along these lines.) At the very least, it's nice for when you're unsure about the strategy on something and want to test it out and gradually work up to the highest difficulty level with a group.

In general my suggestion to your friends, in perfect seriousness and kindness, is that XIV probably isn't the game for them - different forms of entertainment will appeal and be tolerable to different people, and an MMO like XIV probably just isn't a good fit. Please refer them to the 'A Word To Our Players' message that pops up at the opening screen to FFXIV. However, I feel the basic idea has merit regardless.