Originally Posted by LifeInAnalog
...probably falls under your "tried all the obvious" courses of action, but the only way I've ever universally changed the fonts is through jrummy's "Root Tools" ...though I haven't tried it on AOKP yet.
I think I finally got it. I had taken SonySketch (desired font) regular, bold, italic, and bold-italic, and masked each of them with the proper name found in the /system/fonts file and made them into a flashable .zip but this didn't fix it. Today, I just dropped all of them into a folder on my SD card, and used Root Browser to copy-paste them over from my SD to /system/fonts and rebooted...VIOLA! The entire phone has been changed. I'm going to try making a flashable .zip again though so that it's easier to share.
EDIT: Here are the new flashable .zip's. I just took the Steel Droid 5 .zip that was on my desktop and erased everything but the fonts file then duplicated it, keeping META-INF but replacing the stock fonts in the 2nd .zip with the renamed Sony Sketch fonts. Tell me how it goes if you're interested.