You can drill the bracket and plug weld the element into place. It would get rid of the mig tracks, let the element float, and not interfer with the bracket laying flat against the wall.
Or counter sink the hole on the back side of the bracket,and pein the rivet to fill the hole then grind flat.
Or use a close fit hole, heat the bracket and element, and insert a cold rivet. When the metal cools, it should lock the rivet into place. Use a little ox/ac local heat on the rivet and pein it into a countersunk hole, then add a little decoration on the rivit head to make it look pretty. On the top joint you can make a second head on the rivet so it will show. I think they said to use one and one half times the diameter of the rivet to form the head. A set tool would form a better head than just the hammer.