I know that one thing you can’t do is have custom tabstops for text. The plugin https://github.com/SublimeText/ElasticTabstops is unable to completely implement elastic tabstops, and its README says that “Limitations in Sublime Text's API make it virtually impossible to use elastic tabstops with spaces.”

Though neither Vim nor Emacs currently provide all the APIs necessary for elastic tabstops plugins, either. They only have the possible advantage that since they’re open source, such support is a little more likely to be added.

Friction + capability + turtles all the way down.