I recommend against making this a 3d part as in it's most crude form it would have at least 3 triangles per stud cone on the rim, but it would take 6 triangles per stud cone to make a difference.
There must be 100 stud cones on the rim in that shield.
That's 400 vertices and 300 surfaces just for the rim, per every such shield in the battle map.

Performance wise this would have the same effect as permanent arrows.