Interesting concept though it might get dangerous if you forget to empty the AMA when you tack. Personally it's easy for me to just hike out on the tramp and use my tiller extension ( a simple piece of PVC water pipe with a rope loop on one end that took all of two minutes to make and cost about $.50 cents to make.)
However if I were to design something like this I would use a two foot piece of 1/2 inch PVC and an elbow. I would drill and tap a hole in the center inside of the AMA wall about 1/2 or 3/4 up from the bottom. I would attach a line to the front of the 2 ft PVC so it can be raised. When you want to fill the AMA you lower the end if the pipe into the water before tacking. Your forward motion will fill the AMA with water. At the same time you would open a dump valve on the other AMA to start draining. It will likely take a while so will likely need to pedal for a while during your tack while all this water transfers. Once the AMA is filled you can adjust your sail for full power. Mounting the dump facing rearward near the back might create a vacuum to help drain the AMA faster.
If you wanted to get fancy you could have a weighted flexible hose inside the AMA attached to the inlet tube( like in a fuel tank). By doing this the AMA will fill while the 2 ft PVC is pointing forward, and drain while facing backward( via suction from your forward motion). This would eliminate the need for a separate dump valve. Basically it would all work with one control line that swings one tube forward and the other back then alternate. Might even work, but I'm not going to build one because it's just way easier to hike out.
In my opinion a much easier option would be to mount a 1/4" x 2" inch piece of polyethelene sheet about 4 ft long on the outside wall of the AMA side. It would be near the top of the AMA in the front and about 3/4 down from the top at the rear. With one on each side of the boat (outside of each AMA only), the foil in the water would create additional lift on your buried AMA. Totally automatic and simple ( no controls) with no weight penalty, no moving parts, and a lot less work to make.
According to my calculations a 2 inch wide foil would create about 32 lbs of additional lift at 6mph, and a 3 inch wide foil would create 47 lbs of additional lift at 6 mph. This is assuming the foil is mounted at 6 degrees angle of attack, and is a simple plank (1/4 " thick)
Of course anything dragging in the water will create drag, and may effect steering especially on a TI, which has a smallish rudder to begin with.
With 47 lbs of additional lift on the AMA by using the 3 inch foil you could increase sail area by an additional 30 sq ft (like a jib for example) according to my calculations. It might be easier to move the AMA out one additional foot (so the boat would be 12 ft wide vs 10ft), which would give you a little more lifting effect (about 75 lbs) rather than adding the foil with less drag.
My two cents