if the shopkeepers had like mini storylines to go along with their growth that would be cool. Maybe something like when you buy an item from their shop, you get the option of buying something for them. Since they'd obviously be smaller than the main content, i could see some gag storylines like:
Bartender wears shapewear to appear hourglass when she's actually got a huge belly.
Gym Goer gets fat before/after getting buff like some sort of crazy bulk/cut cycle.
management refuses to ever get Wcdonalds Worker a new uniform so it just stretches infinitely thin as she blows up.