This looks like a fun mod, however it's a bit clunky. (too many items able to be bought etc. and numbers on icons as they improve, should be the other way around ^^) If you somehow managed to make it random what items were available in the shop (max 5 etc.) it would be more interesting, especially as there would be some luck involved, and the more shops, the more possibilities.
If that isn't possible, try tying in some prereqs to city levels and types. (Unique Amulet of fire req Conclave lvl 5 etc. and that would make other items obsolete as well) More options at the bottom, less at the top, and more specialized. Probably a lot of work, but it would be a great mod if you did, and nobody else have tried that.
Random thought, if items have building prereqs, would it be possible to create unit "accessories" that only could be upgraded in said city with said building?