I keep coming back around to the same conclusion, at least for the sub-30 cal stuff. I've wanted to do a 204 Ruger or 20 Practical in an AR as well, but come back to just using the 223 for all of it.
The 30 and 35 cal wildcats (and I guess the 300 Blk too) do offer some performance that you can't get with the 223 though. The Herrett based stuff in particular duplicates the old 30/30 and 35 Rem lever gun ballistics, but in a modern AR, so I see some real advantages there for a woods rifle.
