I believe that adding the canards did require removing the gun. I'd be tempted to look at a Viggen-style installation at about the same fuselage station so that I could keep the ammo drum essentially where it is and change the feed routes to the gun; your fairing for the gun could then fair into or around your centerline pylon. The AVEN nozzles don't, as I remember, look all that different from standard F100 nozzles with "turkey feathers", I suspect there's some difference in engine length that could be duplicated with a short spacer 'tween nozzle and aft fuselage for each nozzle. Though if you want strictly 2-D vectoring nozzles, I'd say to go with YF/F-22 ones for commonality, though materials for export version likely would vary.
Oh, I just checked, I was slightly in error, the gun is on the starboard side of the aircraft and the refueling receptacle is on the port side. It looks like you might could relocate the refueling receptacle one bay aft for the canard installation.