I think 95% of my uses of the triangle shape in Antetype are to make a balloon/tooltip “point”. Since this is a very common UI pattern, and since it’s kind of a hassle to make them manually, and since in Antetype Web they are harder to make with the lack of triangle borders, it’d be awesome to have a “add point” feature for a rectangle cell. This would do whatever behind the scenes CSS trickery is needed to add a seamless point, and let you control its position, orientation, etc.
How would that work with styling? You may want to have a box-shadow behind your main bubble. That is not going to work with the tip unless some elaborate svg clipping path was created. Other than that I support your idea. (Provided I can still add my own styling.)
We have started with SVG drawing, but it is not good yet. You can add vector cells from the develop menu. But no shadow support yet and no way to nest elements or text in the SVG.