I've thought about this for a bit, although I mostly think in plastic. But I think my ideal pot could be adaptable to clay. If I could have any shaped pot, it would have a wide saucer, but deeper than saucers usually are, probably 4-5" tall. The bottom half of the saucer, perhaps up to 3" would be glazed so it retains water. The saucer would be designed to fit perfectly under the rim of another pot. It might have an "overflow" hole on the side, say 4" up.
In my imagination this inner pot would be similar to a net pot, but it could be a clay pot that's unglazed at the bottom (probably glazed on the top half). How I would plant is put a layer of something inert, say LECA at the bottom, and then the rest with bark above the overflow height. When I water, it retains a reservoir underneath the media, creating a moisture zone without making the medium soggy.
For mounting, I'd imagine a half pipe, sort of like a roof tile except with deeper curvature and a half-glazed pocket at the bottom to hold a reservoir and the unglazed part could wick excess water upwards. The plant would be nestled in the inside of the half pipe.
I have no idea whether these ideas would actually work. One day I'm going to buy a 3D printer or commission a foreign manufacturer and give them a try.