Oh BTW, if you do this, there is one nasty Safari bug I ran into which needed a simple workaround. If you have many copies of a particular component on a page, and that web component uses SVG, then the elements within the SVG need to have unique IDs. This is a Safari-only bug that's related to SVG, not the web component API.
For example, say you use a svg button component several times on a page, and there's a filter in the SVG that you use to change the appearance of the button when it's disabled. If the filter tag doesn't have a unique ID, and one of the buttons is disabled while all the other buttons are enabled, then all the buttons will become disabled if you modify just one of them, because they're all referencing the same filter.
It's very easy to make the IDs unique by using a sequence number (as a member of the component class), incrementing the sequence number in the component constructor, and appending that sequence number to the ID every time you call the template function.
After I fixed this problem in my code, I found out that the css-tricks guy had also run into it and he did a whole write-up about it, but he was using React not Web Components: https://css-tricks.com/heres-how-i-solved-a-weird-bug-using-...