New to these forums, just wanted to mention how cool it is that the community has at least partial access to the source code (not sure to which extent) - Civ IV exposing a big part of the gameplay code in a separate DLL is what let to such amazing mods as Fall from Heaven II, so - good move.
Regarding mod distribution, it would be interesting to do the same thing as Cities Skylines and allow the loading of plugin .dlls. Just like in the C:S, RimWorld and Kerbal Space Program communities, modders would presumably use
https://github.com/pardeike/Harmony to inject their code in the functions of their choice for easier compatibility between mods.
Steam Workshop support for those dll and xml mods similar to the game communities mentioned above would be pretty awesome. While some mods will undoubtedly be integrated into the game, not everything will fit, and the volume will eventually exceed the integration capability if the game is at all successful.