This is pretty much what Powas has suggested but with using Market Squad members as middlemen for you guys to do the trades.
However with your idea of it, is there would be a bit of coding from the forum devs to implement that but should be possible to do but it may take them quite a while to add something like that.

It hasn't been officially stated that we are doing that but seeing as there is really only me and Powas and we both support/encourage the idea if you would like to use me as a middleman for a trade I wouldn't mind.