There was a really good video on a similar idea made by kazoocat (or at least, I think that's their name, just look up "what if security breach had five nights" and it should show up) that you can take inspiration from.
Personally though I think that the mega pizzaplex had way too much effort put into it for it to only be in one game + dlc. I feel like steel wool would have really benefitted from approaching the pizzaplex like it was a marvel phase, with 6, maybe 7 games that all take place inside it. Most of them, except for SB, being small scale projects, focusing on showing off the setting, the characters, or the story. The release order being something like this
1. Game that focuses on introducing the setting and characters restricting you to areas where the vast majority of customers would be. The other characters would all have minor roles except for vanny, with the story cementing her as the new central antagonist.
2. Chica focused game, restricting the player to the restaurant areas and mazercise (perhaps with a redesign to better display that it's specifically Chica's area.)
3. Monty's game, Monty's areas. Hints at the Bonnie murder plotline but doesn't give you enough to solve it without guessing.
4. Roxy's game, Roxy's areas. Story focusing on her unusually complex emotions and backstory for her relationship with Cassie, perhaps leaving enough out so that it's still a surprise in ruin.
5. Freddy's game, give him an area specifically for him and access to a select few employees only/secret areas. Introduce the hiding in Freddy mechanic and what it can do. Story focusing on mostly side characters since Freddy is constantly with you. Sun/moon, DJ music man, as well as a heavily increased vanny presence.
6. Security Breach, except with more time, money and ideas, plus a game director that can actually keep the game's scope at a manageable level. All areas available, All primary characters get equal focus. Epilogue showing the downfall of the pizzaplex.
7. Ruin, mostly intact. Minor focus on Cassie and Roxy's friendship and perhaps expanding on it. Major focus on tying up as many loose ends as possible. Better writing to make the mimic's introduction more satisfying and exciting.