I would add Elephants to that list. I don't mind the Xiangqi Horse being represented by a normal Knight (although for experienced Chess players the difference between the two is the biggest stmbling block for playing Xiangqi). But I am not sho charmed by the representation of an Elephant by an ordinary Bishop.

As I pointed out elsewhere, most of the pieces you mention are quite easy to make from a normal Staunton Chess set. I am not sure what you mean by 'Vizers', but I assume you mean the pieces next to the Xiangqi royal piece. They could be decapitated King and Queen of a normal set. (I don't think the 'head' they have here in the photograph, somewhat reminiscent of an old-fashioned coal can, adds much esthetical value.) The Queen's head could then be glued on top of a Knight, (after grinding off the ears), to make an Amazon. The upper part of the other Knight could be glued on top of an inverted Rook to make a Chancellor. A V-shaped cut in the Bishop's head (making use of one of the cut that is aready there)could remove the top of the Bishop, and make it an ArchBishop.

When done carefully, all this would provide high-quality pieces that blend in perfectly with the normal Chess set they were made from, and starting from two equal sets would automatically supplement the number Pawns you ned for wider boards. You would actually have a surplus of Pawns, and a Pawn glued on top of a Knight's base could be another general-purpose piece. (Unfortunately you can't make a pair of those, if you use the other Knight for building an Amazon.)

Biggest problem are Cannons and Elephants. The Cannon's could be made from Knight's bases plus some parts specally manufactured for the purpose. To make something that remotely looks like an Elephant, even in an abstract sense, is a problem in itself.

If we would really want to sell such pieces through this website, the best way might be to strike a deal with a manufacturer of normal Chess sets, to order pieces or piece parts individually, so that we are not limited to the frequencies (or sizes!) with which they occur in normal Chess sets. We could then, for example, use a Bishop of a larger size to convert to Archbishop, and we could buy the Knight heads and bases separately. Unlike plastic pieces, wooden pieces are manufactured completely independently, and not having to assemble the Knights only saves the manufacturer money.

I have looked at retail prices of wooden Chess sets, and some acceptable sets are already sold on the internet for €16,90. (I could even find sets for €7,99 in the toy shop, but they are of ugly design and rather smal size.) This amounts to ~50 cents per piece. In general, a manufacturer should be happy to sell his products for the retail price.