I'm working on belts now, and have quite a bit of room left. I don't feel like I've gotten a solid Standard set after adding some new stuff and converting over the HM2.x gear, so if you have ideas for me, please let me know in the comments.
I am probably going to do Belt-Buckles and Belt-ClipOns as separate sets. There are sooooo many of each, I thought I should probably just stick to actual full (or mostly full) belt-type items in the Standard set, and really go to town on the other two.