@vidak Personally when it comes to blocking malfeatures or simplifying the implementation, I find JS the main culprit. So I'd remove <script> & the handful of elements reliant on it.
I think it could be good to reengineer the form elements to better promote accessibility, which could simplify implementation.
Interactive elements could help webdevs make peace with the lack of JS.
Semantic & metadata elements are to my mind non-issues.
I wonder what you think?