An idea which I don’t know if it’s sensible for LightGraphs: have an exported Dijkstra() function (or type) which, depending on the arguments, creates a ShortestPaths.Dijkstra object or an OtherModule.Dijkstra object.
This means that the arguments for the different Mod.Dijkstra types must be distinct, in particular the no-argument version is available for only one of the types. Or the no-argument Dijkstra() could create an object of a third type which is accepted by both shortest_paths and other_module_algo as a tag for what should be the default parameters for the corresponding Dijkstra algorithm.