The Standard Product Nomenclature System is one of our few international standards in the Kikyo Sector, like the standard cargo container sizes and airlock sizes. It started with Yamatai and most neighbor factions have picked it up out of convenience because it's useful. The most useful thing about it is keeping track of which subsystems go with which ship, for example you can immediately see that any weapon that as a nomenclature Ke-S3-W3900 is something for a Sakura, Plumeria, or Fuji class gunship because those are all Ke-S3-xx or that a Ke-M2-W2901 is a Mindy weapon because it has M2 in it.
If a manufacturer doesn't sell products in the Kikyo Sector, for example in the case of NMX warships, then it would make sense to allow them not to use the SPNS. Also if they don't have familiarity with the Yamataian calendar, which is the standard calendar for most of the Kikyo sector.
If you want to come up with your own factional system (like the US Army's M numbers, NSNs, or project numbers or something) you can do that, But otherwise please just use the one provided.
If a manufacturer doesn't sell products in the Kikyo Sector, for example in the case of NMX warships, then it would make sense to allow them not to use the SPNS. Also if they don't have familiarity with the Yamataian calendar, which is the standard calendar for most of the Kikyo sector.
If you want to come up with your own factional system (like the US Army's M numbers, NSNs, or project numbers or something) you can do that, But otherwise please just use the one provided.