Not sure how to do it with a module, but with a plugin you define its LoadingPhase to be PostConfigInit, which will initialise it early enough to allow IMPLEMENT_VERTEX_FACTORY_TYPE. I know this doesn’t answer your question, but will hopefully give you some hints on what to look for, if you do find the answer please share.
So same as the plugin way, but in the .uproject file instead (ModuleName should match the name of your game module).
Usually what you would do though is split up your engine specific stuff (ie. Vertex Factory code and other rendering stuff) into a seperate module and only load that module as PostConfigInit and have your standard game module loaded normally.