An option in the Game rules that disables every dismemberment except neck dismemberments.

Agree or disagree?

It's called make it into a mod, you don't need game rules for this. Not supported.

Man, it would be interesting if they applied their idea.
We could be the most fun, with a new fighting mode. It is likely to be a lot of fun and funny

Just take a look at the modmaker. There you can change the dismberment threshhold for each joint individualy. Just load rhe mod xou want to change and raise the other threshhold of every other joint stupidly high.
Ask me if you have got any more questions.

It would be more complicated, in my idea, just check out a box in the game rules and *ta-da* you're done.

This doesn't need to be a check box. Making it into a mod on your own accord will take much less time.

For example here it took me a minute or two to turn aikido into decap only.
I set neck dm to 100 and 250. I could upload these to the game if you want.