So my original issue that triggered my empty object suggestion was that I discovered you can't move/reposition a sprite itself while actively using the Orbit plugin on it. So I was looking to make the sprite a child of an empty object and move the empty object with Tween while doing the Orbit.
I ended up creating a 16x16 yellow filled sprite named Empty (to make it easy to see on the Event sheet), making it invisible and turning off collisions and adding the Tween behavior to it, and using the Orbit Pin feature to pin the sprite to the Empty sprite. Now I move the Empty sprite with Tween and the sprite moves with it and can orbit with no issues.
I do agree that a scenario of 1 million empty sprites causing a slowdown is extreme and not realistic. On the flip side, maybe an empty object would be a good project for someone in their spare time as a third party addon.