My concern is not in how merchants work, or even if we are allowed NPC merchants. My concern is in these two things:
How will we combat the long term repercussions of inflation that the money received from voting causes? There is X amount of gold in the world - and the more that people vote, the more that 'artificial' gold is added to the system. The more 'artificial' gold that is added to the system, the less gold in itself will be worth. The less that gold is worth, the more people will charge for goods and services, until - after an unknown amount of time (could be a year, could be two months - depends on how many people vote on a daily basis) - one of two things will happen. Either prices will soar through the roof to try and compensate for the degrading value of gold, or people will simply stop buying with gold due to the astronomically high prices. Ten gold today would be one hundred gold in the future
How is money re-introduced into the economy when goods are bought from NPCs? Think about it - each time we buy a lock, it goes into the pockets of an NPC. That NPC will never buy anything, unless Yotta makes a plugin for it. Since we are constantly throwing away money, this impacts the economy in the exact opposite way that introducing 'artificial' money does - it raises the demand for gold by taking money out of circulation indefinately. This would cause prices to lower to the point where ten gold today would be held at the same value at one gold in the future.
The reason that these two do not 'balance out' (as I'm sure some people will argue) is this:
Locks only serve a purpose to those who need it. If someone has hidden a chest well enough, they do not require a lock. Also, even if someone has a room dedicated to chests and locks each and every one of them, and considering that the room houses 25 chests at the maximum, they would only spend 2500 GN - which can be 're-introduced' into the economy if thirteen whitelisted members vote in one day. Considering that it is highly unlikely that a room to house 25 chests will be created on a daily basis, inflation is a given. If the source of inflation is removed, 'deflation' is a given - albeit in a much slower fashion.
TL

R - We have a problem that could pose a very bad economy in the distant future through inflation or deflation.
"One can concentrate so closely on the words of a sentence that one thereby misses the meaning. As can happen in any area of life. You must never lose focus on the larger landscape."