I don't see the analogy working. It's definitely not as straight forward as taking off a physical part. Just looking at changes since 7.0, there are least 20+ feature changes (this is just looking at the general headlines, if you count individual changes within each one there may be much more). Each one can be deemed an undesirable change in functionality. That can mean 20+ different branches just for 7.0+.
Model S software/firmware changelog
I'm reminded of the Android 4.4 Kitkat restrictions to SD Card write permissions, which Google pitched as a logical upgrade in security (similar to how this is a safety related), but some people felt it was a major functionality loss. It was easy to toggle back if you rooted your device, but obviously no manufacturer nor did Google implement such a toggle.
http://forum.xda-developers.com/showthread.php?t=2684188
There are some serious vulnerabilities in 4.3 that Google said they would not patch, and basically if you did not update to 4.4, you would have to live with it.
Report: Android 4.3 Devices Vulnerable to Bug
Google: Why we won't patch pre-KitKat Android WebView | ZDNet
For the people who didn't like the 4.4 changes, they basically had three choices:
1) Live with any bugs and vulnerabilities in 4.3
2) Update to 4.4 and accept the change
3) Root the device (and risk voiding warranty) and toggle back the SD Card write permissions to like 4.3
There was no 4th choice of forcing the manufacturer to patch 4.3 independently nor a fifth choice of forcing them to offer a version of 4.4 without the new SD Card permission restrictions. People who are familiar with iOS can probably come up with plenty of similar examples. Basically I see no precedent to what green1 is asking for.