Simulate chroot with unshare

I am trying to write a bootstrapper for a minimal, from-source linux distribution. I would like to build in a chroot-like environment. This should simplify packaging. I do not care about security at this point. The bootstrapper should not require any non-standard third-party commands. It would be great if there is no need to be root, either. This is why fakechroot(1) fakeroot(1) chroot(1) is not exactly what I am looking for. Is it possible to fake / using unshare(1) and /bin/sh?