This seems like something that shouldn't be the container formats responsibility. You can record arbitrary metadata and put it in a file in the container, so it's trivial to layer on top.
On the other hand, tie the container structure to your OS metadata structure, and your (hopefully good) container format is now stuck with portability issues between other OSes that don't have the same metadata layout, as well as your own OS in the past & future.
Honestly, sometimes I just want to mark all files on a Linux system as executable and see what would even break and why. Seriously, why is there a whole bit for something that's essentially an 'read permission, but you can also directly execute it from the shell'?
No you can't. If a user can read something, it can execute it. The only thing where it matters is setuid applications where the setuid bit allows the user to run an application as someone else. But it's already a separate permission bit, and frankly, the whole setuid idea turned out to be quite a high-maintenance design in the end, with lots of additional features heaped on top of it to help mitigate the worst vulnerabilities.
On the other hand, tie the container structure to your OS metadata structure, and your (hopefully good) container format is now stuck with portability issues between other OSes that don't have the same metadata layout, as well as your own OS in the past & future.