You should add a command /trade example: say I was to Trade my friend Spurdexy485 I would do /trade Spurdexy485 It would send them something that says sam_drums has sent you a trade and something comes up in red bold that says denied or accept. If they click denied it would send me something that says spurdexy has Denied your trade request. If they click accept I it will pop up two spaces to put things in in the middle there's a green glass pane that says accept once both players put there stuff in the space and click accept. There would be 3 glasses panes that count down from 5 and make a jukebox sound. And both players would get the stuff they traded for and to cancel trade just escape or choose take a item out.
I can tell you right now, that would be hard to implement first off, and second off, the style of the "click to accept or deny" is not really an ECC thing (just for servers that start with H). We do, However, have the / commands for stuff like that.