I am sure something like this has been discussed before but I have been imagining what a decentralized market might look like.
It could not function as a traditional website with an apache install etc as that inherently requires a web administrator. To have the system run without the threat of being malicious it would probably need to be an open-source program. Ideally a P2P solution.
There is no need for a centralized wallet. A system could be devised where everyone controls their bitcoin keys until they are sent into temporary escrow wallets which exist for the duration of transactions.
As I see it there is no way for the solution to provide for proper dispute moderation so the system could be supported by a community of democratically elected (or impeached) moderators which are switched out at regular intervals. A small fee could be levied on transactions in order to pay these moderators. This whole moderator business is the messiest part of the design - if there is a way to completely eliminate the need for human influence, that would be ideal, but probably not practical.
The concept behind all of this is to basically create an exit-scam proof situation. If it was made well enough and supported by a large community, it is something that could kind of take on a life of its own. Properly designed there is no need for high level administrators with the power to disrupt the market - the only power that any person needs to have is in dispute moderation, which needs to be handled on a case by case basis.
What good does escrow do without a centralized and trusted authority in case of dispute?