It seems to be semi-common practice to replace the engine's main options menu.
As of today this feature is blocked - user mods will not be able to replace the main options menu anymore. Instead a warning will be printed to the console and the menu override be discarded.
The reason this was done is that this menu contains critical settings that must always be accessible. Since the options menu and its submenus expose engine features to the user interface they obviously can change at any time a new feature gets added. This sometimes can result in the addition of a new submenu and the addition or removal of new entries. Any user mod overriding this will be locked to the version of this menu of the time of its making, resulting in false bug reports and usability issues.
As such I deemed it necessary to ensure that the internal menu always gets used. If you absolutely feel you need an option menu for your mod, there's two options:
1. Use 'AddOptionMenu' to add to the end of it.
2. Use a separate 'Game Options' menu accessible from the main menu. This is actually the preferred way to do it because it separates game from engine options more cleanly.