you can provide the top level directory where it will extract with the -e command line switch

No, sorry for being unclear, I mean if the archive contains a toplevel folder e.g. binutils-1.0.0, that I can rename it to binutils before extracting (so I don't end up with the binutils-1.0.0 on my filesystem), and preferably in such a way that I don't have to know the toplevel folder name before extracting.

Yeah, exactly the kind of command-line that I would like to avoid ;)

Among other things, it's a shame that there's no dedicated standard-ish CLI tool for manipulating pathnames.

Sadly no, unblob cannot do that. I'll look into it tho.