I think the idea that booking one night throwaways disrupts a whole week for a campsite is a fallacious argument.
First, it presumes that the majority of bookings are for a whole week, which is not in evidence (in fact, at the campsites I'd expect that to be very different than the regular resorts).
Second, it presumes that there is only one person booking such a throwaway, ruining a whole week at a particular campsite, on a given week. I'd say it's more likely that there is more than one such person, and that those persons would probably be distributed through the week, and thus could be accounted for by the same campsite, thus minimizing the effect on anyone else.
And if it affected the bottom line that much, and Disney saw how much people were willing to book a throwaway, Disney could in turn say, "You know what? If you want in to FP+/MagicBands so badly, just pay $50/$75/$100 up front, and we'll let you have early access..."
I really doubt this is going to last long regardless.
As for parking/perks, paying for one night essentially gets you two days of resort perks - parking, room charges, EMH, etc. The exception being Dining Plans (you get credits per night, not day) and FP+ (not _really_ a resort perk, where you can book FP+ up to length of linked ticket/max 7 days).