Then how come Their a Wiki Page About it then? And then People who make Mods to use that information in the Ship description then?.
Well if 3 worth Built By the time of Operation Shadow Hand then I like to see it Buildable in Era 3 as a Second Star Dreadnaught you can build as the Imperial Remnant and all so be able to build it In the GC Form The Ground Up as Imperial Remnant or the Pentastar Alignment or both. And if both now that would be an interesting fight to see.
Dude, it's not like:"it existed so into the mod with it". Consider balance and keeping everyone unique. If Remnant gets a third type of SSDs then they become overpowered. They already have Executors which were more common and iconic, so it would be a bad choice to replace them with the Vengeance either. They have Sovereign which is a category on it's own and you want to add Vengeance too. Not to mention that in Era 3 they also have Palpatine in the Eclipse.
If for players, they can have 6 SSDs in Era 3. For AI, already unlimited since AI doesn't give a thing about build limits and this is a base game problem.
Even if we just say 1 buildable then players already have 7 SSDs available. That is TOO MUCH! Not to mention the AI.
You also have to consider what new does it bring into the game. As I said, it is a differently designed Executor. Their armament was largely the same, so it wouldn't bring anything new to the table.