fullcontrol

Agreed, I would like to be able to specify vase mode as a height range modifier in the slicer, so I could shift back to non-vase mode near the top. 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.

Yes, fuzzy skin does that, in order to create a rough texture. But your idea won't be perfectly conforming to the original shape either, the physics of molten plastic means you will likely get unevenness still. You could consider writing a post processing script, or perhaps experimenting with https://github.com/FullControlXYZ/fullcontrol (not a slicer but a toolkit for generating gcode from python). I suspect that a full on slicer in pure python would be rather slow though. I don't think IdeaMaker is abandoned, but it is closed source freeware.