The recommended way to specify output filename formats is to add your comps into the project's render queue, edit the filename in the "output module" section of the render queue (using something like "filename_[####].TGA"), save the file, and just specify the project file (.aep) on submission.
Because of the way that the "aerender" utility works, if you must override the output path at submission time, you will also need to create and specify an appropriate custom output module template. The custom output module must also be available on all the worker nodes.