Try override this methods for UObject:
virtual void PostInitProperties();
virtual void PostLoad();
Checkers:
FApp::CanEverRender()
FApp::IsGame() // #if WITH_EDITOR
Maybe this get some direction for research.
EDIT: Also check FCoreDelegates
OnBeginFrame
OnSamplingInput
OnInit
OnPostEngineInit
OnFEngineLoopInitComplete