You are going to find that unifying the Tierce (1 3/5) pitch out of a equal-tempered tuned unison rank is NOT going to work well at all...the 2 2/3 is liveable, but the tierce is going to be about 13 cents (13/100th of a semi-tone)off pitch and will NOT blend and produce the 'sesquialtera' sound that you desire. Keep in mind that it's not only the wind chest that needs to be built, but also you will need a reservoir and a quiet blower so that you have a steady regulated source of wind pressure, AND you will need the keyboard and contacts and switching system (you could use 2n3055 transistors and ganged switches for the unification).
Like the others, consider whether you want to be PLAYING the organ or BUILDING the organ. most people that I know that have small pipe organs end up working on them more than playing them, always trying to "tweak" the tuning or fix something that they otherwise would live with (various flaws).
Rick in VA