Leaving that to your judgment.
Another reason for just 1 package:
You can share more common code / questions.
Alternatively, if you prefer two packages, why not three? Perhaps these common code / messages (disclaimer, language selector) could go into a whonix-(gw|ws|shared)-setup(-???) package?
Just saying, I don't want to convince you.
Would you like to put https://github.com/Whonix/Whonix/issues/15 also into whonixsetup wizard? Nevermind about that. We can also do that much later.
Another obvious comment I have, I would like to have whonixsetup wizard being as brain dead "click though" as whonixsetup. I mean, for someone who accepts the disclaimers, uses ENG/US, wants to use Whonix stable repo, connects to the public Tor network (the most common defaults), they'd only need to click "next".