While I also agree features such as vcs integration, intelisense, inline documentation are worth while, They can be in other packages. I think a package should do one thing and do it well, not try to cover everything.
I do not know of which features you need, but I know there is a git package that works decently, “SublimeCodeIntel” provides some more “intelisense” like features. I currently don’t know of any documentation related packages.
Thanks for your notes so far, currently I am trying to decide on the breakpoint interface. My first idea is to have a icon show in the gutter, but i’m not sure what beyond that. Should the icon be different for different types of breakpoints? Should I apply some highlight scope to the line itself (this then messes with peoples themes).
For showing variables defined, I haven’t decided on the best Sublime-UI to use. The most obvious idea is to use a control like the sidebar, but unfortunately that is not available to the API at the moment and i know of no plans to make it so. The other option is to have a quick panel, so you would activate it with a keyboard shortcut, then see a list of contexts, such as global, instance or local variables, which you can select. Then it would show another quick panel with each variable name, and possibly its value.
If the variable is an array or hash type it would have yet another child quick panel (this can go on forever until the panel is closed.)
If the variable is a string, i would limit how many characters are shown on the panel itself, and when the vrible is selected a temporary window could open with the contents.