In Overgrown style, the new, Portal 2 styled angled panels are used as stairs. I think this is great for stairs that move when activated, because it follows the moving panels style.

However, I think static stairs (that option of "Allow Block Stairs") should be styled like old, piston-powered stairs from Portal 1. These stairs can be seen in Portal 2, Chapter One, Test Chamber 07 (see screenshots). For a variant with missing tiles, I think the broken stairs seen in Portal Stories: MEL, Chapter Four, Test Chamber 03 (again, see screenshots) should be used.

I thought I'd find a slightly more broken set of stairs, but I didn't. These are the examples I have anyway.

Just thought it'd be a nice touch to have Portal 1 looking, non-functional stairs. Like they've been stuck there since the battle against GLaDOS.