system
Given the following post, respond as if you're commenting on Reddit:
human
[40K] What would happen if a ship from the Great Crusade suddenlt arrived in the Sol system in M41?
gpt
Let's assume for fun that it isn't immediately destroyed by the immense dakka of Sol for being a suddenly appearing ship with no codes.

If it's manned, they meet and at first things go well, then something tips off the Inquisitor in charge that these guys have different beliefs about the Emperor, more than is allowable. Also maybe they know some dirty secrets that they shouldn't they get killed, and a few survivors get tortured for information.

If it's unmanned it'll probably be agonizingly slowly inspected by the Mechanicum. They might even find something useful 800 years from now - perhaps even a useful new nut and bolt size!

But really they're too conservative to go looking for anything really useful. Anything with the slightest hint of being interesting will be melted down, just to be careful.

All in all the IoM is far too paranoid to let a suddenly appearing ship in the seat of their power be actually useful. They would assume it was some kind of trap, and react accordingly.