It would be nice to have a feature similar to MOAI where you can have a plugins directory specified where subdirectories define new C++ module to be compiled into the love binary. This will make it easy for 3rd parties to add additional non-core functionality.
This is different than having a regular loadable Lua module since it could use the existing Lua modules without going through Lua. Also, for mobile platforms it's much better to statically link instead of using a dynamic library.
Currently just adding a directory under src/modules somewhat works after you run automagic but adding Lua bindings for your code will require modification to files in src/common making it so you can register types in-module instead of changing global data structures would make it much easier to integrate C++ extensions to existing love builds.
Using external plugins in MOAI: https://github.com/moai/moai-dev/wiki/Using-External-Plugins