Most debootstrap wrappers allow you to inject arbitrary options and let
you customize the target suite and the mirror. But very few let you
specify the "script" parameter (the specific wrapper that is causing me
problem right now is live-build 5.x).

I would thus suggest to offer named options for all optional positional
parameters... so that we can rely on the fact that we can inject arbitrary
options to compensate.

Note that cdebootstrap already made such a choice, since it does not have
a script positional argument but a --suite-config option.

So maybe it would make sense for debootstrap to have --suite-config=foo
actually run /usr/share/debootstrapt/scripts/foo and that way you
would (partly) solve #742672 too.

And --mirror=url too although it's ok if you don't want this option.