[member="Mabbik"]
The only rules on lightsabers are that, before an NFU can use one, they have to have a dev thread showing development of that skill.
As such, you may choose to start with your own lightsaber or no lightsaber. Or use a training lightsaber while building and developing your own. There's no right or wrong answer, only your own preference.
If the lightsaber is a traditional weapon that conforms to screen canon, there's no need to submit it to the Factory. If, however, you want the lightsaber to have some unique properties, then you'll want to submit it to the Factory so that those abilities or attributes can be approved by the Factory Judges for use on the board. Such a submission may or may not require a dev thread, depending on the attributes requested and how much they vary or are unique from the traditional lightsaber.