My primary issue at the moment is that I have a frame that, while perfectly fine in regards to seat tube and head tube length, is causing me issues when it comes to top tube and reach, resulting in having to set it to uncommon degrees to compensate.
I'd like to change to a smaller geometry that only requires me to compensate with a longer seatpost, leaving me open to better options in regards to stems and setbacks.
If you like a longer head tube, then you'd go for a WSD in that style of bike. For example, the Felt Z has a tall head tube, and they make a ZW. I think Specialized (and I'm sure others) have WSD versions of their frames with taller head tubes
Unless you have the maximum (generally ~40mm) of spacers under your stem, you really don't need that tall of a head tube. Keep that in mind. Long head tube + short spacer stack = Normal head tube + tall spacer stack. PLUS, you can get a high rise stem if that's what you need to get a frame to fit. It's not "pro" looking, but a perfectly acceptable fit option. The pertinent measurement is the saddle/bar drop and there's more than one way to achieve it.
 just looked at the photos linked in your OP - and scrolled down to look at current set up. You're NOWHERE NEAR justifying the need for a tall head tube!! You have your stem at minimum height fercrissake! Based on that photo alone, I can't imagine the head tube is a problem. That, and based on your dimensions, you should simply be looking for a smaller frame (say a "52" rather than a "54" - but looking at the top tube length to make sure it's shorter), and then just use normal spacer stacks and/or stem flipped up to get the handlebar height you need.
It's really too bad that upwardly angled stems are so scorned because they really make more sense than a tall spacer stack and are a cheap way to make a frame fit that is perfect except for the head tube length. Alternative is custom frame, most likely.
The zero setback post was something I switched to in effort to shorten the reach without much regard to it's effects on my legs. I would like to move back to a setback post.
Thanks for the advice on WSD. Going through lists of frame geometries I actually did come across a few that would work.
So, it sounds like you did a self-modification with the zero SB post after you'd been properly fitted? Therefore, the bike you have really doesn't represent a professional fitting, but rather an erroneous modification by you that messed up the fit. It's one of the most basic fit factors - you adjust the seat and then adjust the stem.
Interestingly, you might find that re-placing your seat in the proper position will make you more comfortable with a longer stem. "Might" being the operative word. When you're in the right position over the pedals (and it varies depending on personal preference and riding style), you have much less pressure on the hands, and sometimes it might make you feel more comfortable stretched out a little more.
But at your height, my guess is you need a smaller bike that has a shorter top tube and as tall of a head tube as you can find. Good luck!