@Paul: That's what I figured. ;-) I was thinking that perhaps requesting the changes I mentioned might be more palatable to Apple than a flag in Info.plist. An extension to the disk image format (proprietary, and under Apple's control) or adding a hidden file (which could be ignored by older versions of OS X / Gatekeeper) seems like it'd be less invasive.

Not that I'm particularly concerned about political correctness! I'm just thinking of ways that could address the use case you outlined in a way that might be more likely to get accepted/implemented.

In any case, I agree with you. As a user who always drags his apps into "/Applications", I still recognize that many users don't. Packaging apps as special directories is elegant, and it'd be a shame to lose the flexibility of launching them from anywhere in the file system.