That wouldn’t help much.

You can get the same effect already if you expand subgroups manually. Of course, that makes large userbases difficult to manage. You could reduce the burden by generating /etc/groups via a preprocessor or some such.

So this is proof by induction that nestable groups do not actually expand the expressive capabilities of the Unix model. They could make large userbases easier to manage, but everything you can express with them is expressible without them as well.

ACL systems OTOH actually allow mapping scenarios that the Unix model cannot, and won’t be able to with nested groups either. Of course, they are also hard to handle and will fry your brain…

Makeshifts last the longest.