Grilled veggies on the JOE are outstanding, especially the veggies that you mentioned! They blow oven roasted veggies out of the water! For my tastes, when grilling veggies on a kamado, I prefer to control the heat with the bottom vent, leaving the top vent wide open. You want a pretty hot fire so this works well. The reason I do it is because I do not like holding smoke back in the kamado when cooking veggies... the smoke flavor can overtake the veggies IMO. With the top vent wide open, this doesn't happen
Oh yeah, if you don't already have GrillGrates for your JOE, do yourself a favor and get some... they make a huge difference for certain types of cooks, veggies being one of them.
Would love to see pics of this cook (hint, hint)