Depends on the archive type and how the vfs/extfs code was implemented for it¹. It also depends on how the archive is treated if it is compressed container, which can be seen by looking at how a .tar and .tar.xz are handled for example. The zip handler is probably the easiest to understand, as it doesn't need to contend with external compression wrappers and is a simple perl script. (In some cases it would probably be nicer if it did extract the entire archive to tmpfs, such as when you independently pull a few files from a massive .deb for example)
Implementing your own extfs scripts to wrap a simple menu around some task can be really useful, far beyond basic archives. I wrote one so that I can shuffle my todo list priorities by moving fake "task files" in to different pseudo-directories.
Maybe, but I'm not sure if there's much benefit to that. The most inefficient part of the inotify or fanotify solution is that you have to walk the file system before monitoring can even start, because you first need to know which folders and files are there to begin with. And unfortunately this can't be avoided with eBPF.
