Can-Am went throttle by wire several years ago, and it took a lot of getting used to me (they have since made it better on newer models). The throttle is super sensitive and not linear like a throttle cable. You have to learn to make your leg absorb/anticipate bumps so that the shock doesn't...
I don't think anyone has removed the headliner yet. Please keep us posted what you find out when you get yours. What speakers are you thinking about getting?
You might kick some tires on a 2024 model to see how good of a deal you can get. It might be worth it if you can save several thousand dollars on a 2024 model and get instant gratification.
None of the manufacturers do it, to my knowledge, and I don't understand why. I need one on my Defender, and it's more of a pain to install than it should be.