I am trying to write the Python BPY -code inside Blender and noticed some editor -mode (source) and, instead of reinventing the wheel, I want to use my Vim -syntax-highlighting-etc inside Blender -text-editor. So how can I use Vim inside Blender?
You can write scripts either in an external text editor, or in Blender's built in text editor. Move to a panel you wish to change to be the text editor, click the editor select button and choose "text editor" (shortcut) SHIFT+F11. Click the + New button at the bottom. If you want, you can enable line numbers and syntax coloring with the buttons at the bottom. Create a new script with File → New, paste the code below into it, and save it. Or alternatively, paste the code below into a file, and open that file with File → Open in Blender. As name choose something with the extension .py, for example wikibooks.py. Put it into Blender's user scripts path.