I did think about creating a subclass of CssLayout, but I thought it would be a bad idea to (just) override addComponent to add a wrapper-layout around the component. That would for instance mean that getComponent(int) would return the wrapper component instead of the actual component that was added.
To create a workable subclass I assume I would have to add the v-slot div in the client-side part of the Layout, and, frankly, I’m not ready for that yet. Also, it seemed too much work to save just a few lines of code.