I know that this is always a sensitive topic, but I'm going to ask anyway.

Let's assume I was using the following rules:

- armor and shields provide bonuses to AC
- natural armor provides DR, not AC bonus
- DR from NA can never drop damage from a hit below a minimum of 1

What would be the obvious problems with these rules?

(And please don't freak out... it's not a suggestion for 5e, it's just a question. We already know that NA = AC bonus as usual in 5e)