I think you're trying to over complicate things, put the plate back to central, but slightly lower, maybe even fit a square type plate, as a US spec car would have. Make some brackets up that mount to the bumper, but hold the plate 20mm off it, brackets should be hidden, and plate attached the the brackets with sticky pads, rather than screws... so it appears that the No plate is floating in the air, just in front of the bumper... Less is more!
Altering that plate in any way, would just look naff!
Thom