While away from all of my physical circuitry and components, I decided to create a better PCB that would actually function as a wearable. The new design is 40x30mm, compared to 40x60 for the last design. The final assembly is about 20mm thick though, compared to 5-8mm for the previous design (without the battery). With the battery, we're looking at around 25-30mm, depending on the battery strength I'm going for. Meh, I guess you win some and lose some.
Speaking of batteries, I've calculated a very rough preliminary current draw at around 150mA, with the Teensy doing around 100mA, the HC-05 doing 40mA, and the AD5933 doing 10mA. The multiplexer's current draw is basically negligible. Because this is a prototype, I might be able to get away with a 150mAh battery, and the 302530 is looking promising.
Next, I'll work on the FPC electrode design and the enclosure.