Gameplay preview: https://youtu.be/ZgFlZszci2Y

Savegames are supported. Simply save inside the doom engine and then save the Factorio game. Autosaves every 180 seconds.
Upon loading a Factorio save, the Doom engine loads your savegame automatically straight away.

To keep your Factorio UI controls working while maintaining immersion, you should rebind in settings->controls->panels->toggle menu to shift escape.
This way the mod can use escape to navigate the doom menus and you can use shift escape to control Factorio menus.
Of cource you can rebind the mod control keys as well. There is no mouse look support due to modding API limitations.