Nelson has already said you will be able to script with Blueprints though Blueprints are very shit and it will be more of a Workshop type of thing seeing its not actually modding because its just using prebuilt bits of code that Nelson has done for Blueprints
Blueprints definitely similar to other moddable UE4 games, as for C++ I’m okay with opening up my C++ source code it’s really just a question of getting it set up in the Epic Games launcher (required by Epic’s ToS) if a binary editor + compilation required copy of the source files is possible.