I don't view Franco as being any better than Herrera (much worse, historically), nor Kingery/Crawford as being that much better than Williams or Quinn (though they have more upside, assuming Quinn is never a full-time player).
They are all needs. Sure, you can get by with those infielders. You can also get by with that OF once you sign another one, doesn't have to be Harper. The main thing is outfielders are less scarce than all-star caliber offensive shortstops. They will still get one. Though if they whiff on Machado (and still trade Santana) they could also find another 3B option as the second bat.
Also, you have to consider defense. Boras believes Harper will go back to being a plus defensive player this year (which of course he has to say) so that's important, but just getting "2 bats" isn't going to fix things.
I guess I think signing Machado plus a good non-Harper OF is going to be a better team than signing Harper plus a another less-good OF, because that's how I think it would go.