Hi Mat
It's a good article. It describes how to emulate position: sticky with JavaScript. That's the technique we'd use if we were to create some sort of position: sticky widget.
But the approach that might be worth exploring first is to drop in an off-the-shelf polyfill for position: sticky. Because of the ropey browser support there are quite a few that are designed to be dropped in as a simple <script> tag that magically fixes things. A quick Google suggests that this one is popular:
https://github.com/wilddeer/stickyfillIt'd be a fairly simple task to research the available alternatives and try them out. If necessary, I wouldn't be against small core changes to accommodate the needs of a polyfill plugin.
Best wishes