So, when all's done and the feature is finished:
Users can have multiple trades (up to 5) open at the same time, but only one with each user (i.e. I can open a trade with anski, but I can't open a second one with him without finishing or cancelling my first)
Users can trade up to 10 pokemon at a time. Either 10 for 10, or 10 meh ones for a legendary or something. Both the number of pokemon and max simultaneous open trade limits are easily changed.
As a trade is ongoing, either user can change their offer - this forces both parties to re-confirm the trade though.
You can open a trade with another user who either has you on their friends list, or have set their PC option to open trades. Each trade will have its own unique ID / page that only the two relevant parties can access - the user who opens the trade essentially uses the page as an "invite" link - the tradee can accept the trade and start it going when they visit it.
On the trade center homepage, at the top will be 2 lists - trades you're currently involved in, trades you've started. Under that, a list of recently completed trades. Finished trades will be logged and public for all to see.
I also plan to show a recent threads list taken from the yet to be created RMRKMon trading subforum
That about sums it up, I think.