You literally cannot mess with your emissions system legally… nor can you disable or modify certain safety systems (seat belts, etc). Software that goes into vehicles requires validation testing. You might be fine doing 1 off things, but there will never be a “flash able” car on the market that let’s you bring your own software, and honestly I’m good with that. I don’t need your massive multiple ton machine bluescreening down the highway or locking up the breaks randomly because you installed the wrong module.
Less dangerous in the box. Box is shelter from the storm. Well. Not Milton, but smaller storms, surely?