This could be solved if they made more vendor booths that were a little more generic.
Something like the Realm of Magic booths, where they have a version that looks like a building, except less overtly magical.
You could have booths that slot into a wall, that resemble storefronts. Your Sim could enter the store, talk to the vendor, and buy groceries (ie fresh ingredients), new unlockable video games, or unlockable clothing. Something resembling the stores in the Sims Freeplay's Sunset Mall:
https://1.bp.blogspot.com/-5GfgVqAUJt4/VMfzn6jmayI/AAAAAAAAACE/PKBD6BbTM_k/s1600/image1%281%29.JPG
With something like this, any lot could become multi-purpose, to an extent. Own a retail lot? Now your business is one of several, in an actual mall.
Going to the gym? Why not stop next door first, and buy a smoothie?