Wouldn't it be cool if RStudio addins could:
* Open in a source editor tab, rather than the viewer pane (usually small)
* Configure keyboard shortcuts
* Access IDE state, e.g. command history
* Be browsed and installed natively from an extension repository
* Etc.. just be more like source editor tabs or quadrant tabs.
At the moment issues raised on the rstudio/rstudioapi GitHub repo can take many months to receive a reply. I assume this is indicative of the priority of this feature. That's a shame, because IDE/Editors that foster a strong extension ecosystem tend to do well. Look at Vim, Emacs, VSCode, Sublime text, Atom, Eclipse etc... All of them have powerful extension mechanisms in common. I'm particularly excited about the extension system in the soon to be released Jupyter Lab. Their PyData Seattle video is worth a look if you want a glimpse of what RStudio + First Class extensions could be like.
As a brief motivating usecase: I'm playing around with interactive graphics in Vega-lite. I dream of being able to pass data from my R environment through a Vega-lite vis spec in a seamless way, to enable rapid iteration on graphic ideas. A first class extension mechanism could provide for this.