I guess if your Air Force does not need to fly halfway around the planet, the G550 makes perfect sense!
Just to Iran and back.
I would guess a small tanker based on a business jet would be much easier to "hide in plain sight" in the air traffic in and out of the Gulf States than would something based on a large commercial jet platform. That and you could pre-position in a friendly emirate while allowing your host to maintain plausible denial of supporting an attack on Iran.