I have reskinned damaged capsules with aluminized mylar unrolled from film capacitors. The lower the voltage rating, the thinner the film is.?The capsules have sounded fine, though likely not good as new.
I tried making capsules with perforated aluminum sheet as backplate, Scotch tape, and mylar film. They did pick up sound: poorly, not as well as a cheap electret. Like you, I wonder how shape and backplate geometry affects tone. Your method is better because you can isolate the active area of the backplate by etching, and reduce the parasitic fixed capacitance. Good work!
The resistance of the diaphragm doesn't matter much, especially if signal is taken off the backplate. All it has to do is hold a constant charge.
