How many automobile manufacturers give dealers the freedom to modify cars any which way?
Every single one of them, in my experience. Sure, they might charge a lot more if I want something weird. But they'll put whatever wheels I want on it. They'll put whatever tires I want on it. They'll have it where ever I want to pick it up at. You want different seats? No problem. Tinted windowss? Can do. A chain-link steering wheel and dingle balls? It will take a week extra and they'll charge you for installation. They are only TOO willing to sell you a car and charge you for their mechanic's time.

Don't you think there are valid reasons for that?
Yep. 'Cause there's competition for your money. If they don't do it, some one else will.

Even if a vendor has had problems with brand confidence in the past, do you think they should be required, for any reason, to abandon practices designed to protect it?
Nope. Give the customer what the customer wants. But, then again, if the car spontaniously bursts into flame, you can sue the manufacturer. Who do you complain to when your computer crashes?