The answers you seek lie in ConfigCacheIni.h and .cpp
I see how to update individual section from memory to file:
/**
* Update a single property in the config file, for the section that is specified.
*/
CORE_API bool UpdateSinglePropertyInSection(const TCHAR* DiskFilename, const TCHAR* PropertyName, const TCHAR* SectionName);
But you want to go the other way
Closest thing I can find to what you want is
static bool LoadGlobalIniFile(FString& FinalIniFilename, const TCHAR* BaseIniName, const TCHAR* Platform=NULL, bool bForceReload=false, bool bRequireDefaultIni=false, bool bAllowGeneratedIniWhenCooked=true, const TCHAR* GeneratedConfigDir = *FPaths::GeneratedConfigDir());
How about you run a few tests, or poke around in the engine code, and see if you can find an example of reloading an ini from disk? Then I could add that code to Victory Plugin