How to make The Prius Plug-in (Prime) actually worth it

Regen first, then engine generated only as the band needs it, not the other way around. That distinction is the whole point of what I'm describing.

First, to be clear about what I'm actually doing: nothing I'm proposing defeats Toyota's BMS or any other system on the car, and I don't intend to modify anything. Right now I'm collecting data and thinking out loud. I'm not looking to lose my warranty, and I want to be plain about why, that coverage isn't a favor Toyota does me. They took my money when I bought the car, and the warranty's cash value is built into the price I paid. It's not a charity service, it has real value I already paid for, and I'm not going to throw it away. This is observation and discussion, in the hope that Toyota might actually do something worthwhile for their customers and their cars.

On the warranty doctrine, you're probably right that under stressing components to clear the warranty period is the operating philosophy. But that's my argument, not a counter to it. A conservative band chosen for fleet wide warranty math isn't the same as the optimal band for a given car, and what I'm seeing in my own data is that the pack runs cleaner and accepts regen better in a lower window than the factory strategy parks it in. I'm not saying Toyota engineered it badly. I'm saying they engineered it for their liability exposure, which is a different goal than what's best for my use case.

The refinement point is fair too. Toyota didn't chase serenity because the buyer didn't pay for it (even though the Premium XSE is in that Territoryprice wise). But that's a calibration choice, not a hardware limit. The hardware can run quiet and electric at low speed. The software just doesn't prioritize it once the plug-in charge is gone.

Where I'd push back is the "thrashy engine and a more stressed battery" prediction. That's the opposite of what a lower, gentler band does. Keeping the pack in a window where it takes regen cleanly is less stress, not more, and the engine comes on less in town, not more. I'm not dragging the pack to a hard floor and holding it there. And again, the car's own battery management keeps full authority the entire time.

On the GR Corolla denial, point taken, and it's exactly why I'm staying in observation mode and keeping everything stock. There's a real difference between reflashing pack management and simply studying how the car behaves. I'm firmly on the studying side of that line.