First of all you dont need to fire up an additional program. Editing an
image with an integrated editor would be much smother. You could see the
complete context your raster images is used in and you dont have to
reimport the image after changing it with an external program.

I would also prefer if the functionality of using external editors would
improve. For example on linux use inotify to get changes of linked
images and reload them.

If it would be possible to embed the gimp into inkscape it would be a
really cool thing :) Or the other way around: have an svg as an layer
within an gimp file.

Greetings,
Florian Ludwig