I looked at the model on printables, and have a followup question: why does the slit go all the way through? You can make the first few layers print normal and solid (in fact this is very common), so I'm slightly confused as to why you didn't (it would probably increase the strength a bit).
I have a long love affair with vase mode and abusing it, and always saving time/weight is my main goal, like in this other case: https://makerworld.com/it/models/840291-vase-mode-gear-phone...
Your blog post made me thing that we would almost need a specialized vase mode site for models of that kind :D Moreover, there is no reason why the top surface could not be closed with bridging. The slicers have a lot of odd limitations in the context of vase mode.
If you want full control though, you might want to look at https://github.com/FullControlXYZ/fullcontrol (using python to directly generate gcode). Perhaps a bit over the top, but their examples are cool and show things that can't currently be done any other way. You could definitely switch back and forth between vase and normal with it.