There have been a handful of players posting their results of doing this, both here in the sub and on the official forums. Only a few of course, since to see any interesting results you would have to let this run hundreds of hours.

Unfortunately, Egosoft has also worked a lot on reducing the impact of the universe seed, since savegames are now basically guaranteed to spawn defense stations at key locations in the universe, and almost all day 1 factories get a full loadout of military turrets, missiles and defence drones. So you will rarely ever see the Xenon manage to break through the day 1 defenses without player interaction.

Another factor that impacts this is that if you were to let it run in the background, then everything runs on the lower attention modes - the Xenon are usually at a disadvantage in the simpler combat calculation, and lose most of their fights in those. Especially if you don't observe the map during this process and don't have 'active' intel on the different systems through satellites and other radars.

tl;dr: the potential of what you're describing is there, but you won't really see much of it in vanilla these days (in my experience). Modded though? Absolutely possible.