I royally screwed up, I thought removing some unused vehicle images would be fine. Wrong.
I BROKE ALL YOUR SAVES, AND I AM SO, SO SORRY!
The good news, is much of Patch 1.1's fixes needed a new save, but also that I have learned not to remove “unnecessary things” for the sake of optimisation in RPG Maker MZ.
If anyone has lost a New Game Plus save, send me proof of having Dark Lady 2 and the error message, and I'll work something out with you.
P.S: I actually can't work on the game right this moment, as I am currently in between computers, my new gaming PC will arrive in a fortnight, and I've converted my current PC into a Linux workstation for some projects. If anything crops up, let me know on the Steam Forums.