I've been using the importer for different things.
-visualization and animation of toolpaths
-making paths non-planar
-applying weighted 'fuzzy skin'
-mixing gcode from different slicers (using curas tree supports with slic3r only features)
The github wiki has more info about some uses cases.
I experimented with storing feedrates, extrusion rates and other meta info inside each vertex of Blender. One way is to store them in vertex color maps, this way you could edit them by painting over them. The paths need to be meshed/have face loops for that, which means you have to convert back to single paths when exporting.