I think my strategy is going to be to start a somewhat small with a bare-bones inventory system, and then work out from there. As you all see what I'm making and start using it, you'll hopefully see what possibilities start to open up and you can give feedback as we go.
That'll be the best approach, in my opinion, because there are so many facets to this kind of feature and I'd like to try to incorporate the wishes of everyone. We want to have the best trading system out there.