Linux also has "mount -o bind", which corresponds to Plan9's alternative to symlinking.
Same problem applies to one of Plan 9's key design features: private namespaces.
I'll quote jwz: "Convenient though it would be if it were true, Mozilla is not big because it's full of useless crap. Mozilla is big because your needs are big. Your needs are big because the Internet is big. There are lots of small, lean web browsers out there that, incidentally, do almost nothing useful. If that's what you need, you've got options... "