Most of this seems to boil down to a misplaced sence of entitlement. Reread the EULA and SoD Rules and FAQs. No where does it say each player will be provided with a vendor.
Its not 'fair' but then life isnt. Think of it this way: Is the management of your local mall obliged to make accomodations to McDonalds when it wants space in the food court? If the management deems that the A&W and Burgerking booths provide ample opportuity for shoppers to have thier burger needs met they are under no obligation to provide space. And does Starbucks have to give up their second outlet at the opposite end of the mall just because Seattle's Best wants to target the same market? How does this translate to SoD? It is an entity owned by a person (or people) providing a service (which in the case of SoD you are likely using for free).
Wiz and Co already spend countless hours developing content and debugging exsisting systems. It would be nice to see the vendors held by inactive accounts freed up but imposing restrictions and limits on how players use vendors would be assinine. There are already a large number of vendors in game and they arent broken. Id prefer to continue to see new content and have real bugs dealt with before they spend time trying to reinvent the wheel.
If you dont have a vendor there are other options besides /auc spam. Even when they first arrived in game and there were still vendors to be had I had 2 friends with items for sale on my vendor. Bulk sell stuff to someone with a vendor. Get together as a guild and have a vendor that members can place thier items on. Threads in forums work well too and are searchable. /auc the URL to your thread once an hour.
As for the other uglinesses such as gobbling up multiple locations (and possibly selling them for inflated prices), it is just a microcosm or the real business world. You can not expect it to have all the rewards without any of the failings because at the root there is greed. And removing that is beyond even Wiz's considerable abilities.
/edit: Ah, to hell with it. Nuke the current system. Replace with player summonable vendors that spawn tightly clustered around each of the zone in points for the port necklaces so I can just neck from clump to clump and only have to turn in place to browse all the vendors.