I've started work on a factorio instance manager (plan is to also deal with mods). It's not very far allong, but I wanted to show what I have so I could get feedback sooner rather than later. My goal is to effectively reproduce the functionality offered by the curse client for minecraft (now renamed to twitch client last I checked). It should be able to deal with modpacks from some standardised description that are not large in size, so that it will be easy to transfer modpacks to other players without having to upload several hundred megs of zip files to google drive or similar. Currently though, the only thing that's implemented is instance handling, and it only works on OSX (getting it to work on windows and linux should be trivial, I just don't have either available at the moment hence I've not added the code).
The application is open source, built using electron, react, redux +++, and available at https://github.com/Alxandr/automata. No installers/binaries has been made yet (I want more things to work first), but taking the source and running it locally is not hard. I'm not quite happy with the design, but I'm not a designer and this is the extent of my artistic ability unfortunately.