I'm A Banana
Potassium-Rich
I've yet to see anything in the core that makes it even inconvenient to do with 4e.
Well, for one:
No Bards, Druids, or Gnomes. Inconvenient or dang near impossible in some ways (at least going by the core alone).
For two, dragon weirdness with alignments. If the recent preview is anything to go on, being hired by green dragons and fighting copper dragons will not raise many eyebrows in the new edition. I'm pretty sure it WOULD, in Dragonlance.
For three, Golden Wyvern Adepts. Certainly spell-shaping exists on all these worlds, but Golden Wyverns do not, thus mandating an inconvenient name swap.
Just a few examples of things in the 4e Core that don't mesh with, as you say, some of the most generic settings conceived.
