I'd like to add "flipped image" to the pre-flight process.

I've recently had to scour a product catalog for flipped images because a junior designer didn't realize that flipping images mis-represented the non-symmetrical producs. It should be something that pre-flight draws attention to as a potential error, similar to non-proportional scaling.
I was able to install an obscure script that looked for both flipped frames and flipped image content and made a list for you - it was a lifesaver!