StrangerVille premades not to be deleted?

I delete all non-hidden premade Sims in every save (except the one to exclusively play them). I’ve played through that mystery multiple times with no issue, just as @JustinB113 said you will get random townies that take any needed roll. I personally use MCCC to pull from my library for townies, so I end up with Sims I made anyway. I also don’t recall needing any premade lot, the only thing needed is the lab & market stall which you can’t change anyway. In order for the story to start correctly just make sure you have a refrigerator on the lot you fist start playing in (you might need a planter box outside too, but I’m not 100% on that).