I'm not too sure that model would work in WoW. I used to play SWG which had a bazaar (AH) but also players could set up shops to sell their items to others and I think there was also a function letting others sell items (e.g. raw materials) to you through the shop and I think people could also make requests (although that might have just been via mail, it was a long time ago). That was a very different game to WoW and crafting was a much more important aspect.
Space in WoW is very limited and the game is geared towards convenience. In SWG you could buy houses (but these had to be a certain distance away from the cities) and set up your vendor there. In WoW these would either need to be in the main cities (in which case why not just use the AH?) or out in leveling areas (which leads to either a specific target audience for your goods or too much trouble for people to travel out to to check prices). I don't think there's anything rare enough in WoW to make people want to fly out to a location (or several) to check players vendors for the best deal. The AH is much more convenient and not that expensive to use (a main draw of player vendors in SWG was that they didn't take a big cut of the sale unlike the bazaar), you are able to compare prices from a number of different sellers all from the same location.
Also, prices aren't that stable in WoW, some things will sell very well for a time (Silk cloth was going for 30g+ per stack for a while on my server) but due to the ease of farming most things prices can drop quite quickly if more players start selling too or demand drops (silk is now around 5-12g per stack, still high but not amazing). Keeping your vendor up to date with prices on other peoples' vendors would be a lot of work and as you can't really corner a market on anything (due to the relative ease of gathering and lack of risk in crafting) you would probably not end up making any more money than you can through the AH (possibly less if people don't want to travel to your vendor). Not to mention that vendors would need to be advertised somehow, leading to even more spam in capital cities (in SWG you could set up robots to advertise your vendor or some people left afk characters to do this).
If you're interested in making money through selling things then your best bet is to get an addon like Auctioneer (I get very bored of using the AH so don't know what the cool kids are using these days) so that you will be able to see the average price that items sell for at the moment on your server and you can choose to craft the most profitable whilst leveling up a profession (I managed to sell 6 or so
Savage Cloak for 70g each before someone else came along and listed theirs at half the price), if you advertise your craft while in major cities and keep an eye out for people looking for items you could also try to build up a rep on your server for crafting (with the large numbers of crafters this would be hard to do, but then the same would be the case for a static vendor).