I think being able to assign different graphs for different file extensions / types would be beneficial.
I realize you could play with default affinities all day until you come up with a good default values, but it could be really handy to be able to swap in or out a codec with a defined pathing. it would reduce overall setup time and allow installers to use pre-defined graphs for their purposes.
Another option 'advanced' might be the ability to store the graph as %filename%.grf in the same directory as the file and the system could use that graph for that file.
I would think a generic option would be a better choice initially for obvious reasons