Okay, this is live now. Here is the quick and dirty guide for how to do this.
You can do this super quickly using console commands. As usual, you need to use the codes to unlock them. Go to the Pause menu, then simultaneously press LB+RB+X+Y. The box will open up. If you can connect to your Windows 10 PC, you can use this to speed up the console commands significantly.
If you haven't Ascended yet, you need to go to the Island. This will also give you 3 achievements on their own. Note that you will likely lose stuff when you do this. Beware.
Here are the 3 codes. I actually don't know if you need all three for The Center, but you do for those achievements. When you start again, you'll have to respawn.
Now, back out, and go to The Center from the menu. Start by typing in the following codes:
LeaveMeAlone - No one will bother you. Fun times.
slomo 7 - This speeds up the whole world. If it's too fast for aiming or such, you can drop it down to 5 or 4.
Now run up the hill to the terminal. You will need to spawn 6 artifacts to access the Guardians. You can do this on Easy. There are some short codes for a few, but not others, so here are the long codes for all 6:
Artifact of the Hunter -
giveitem "Blueprint'/Game/PrimalEarth/CoreBlueprints/Items/Artifacts/PrimalItemArtifact_01.PrimalItemArtifact_01'" 1 0 0
Artifact of the Pack -
giveitem "Blueprint'/Game/PrimalEarth/CoreBlueprints/Items/Artifacts/PrimalItemArtifact_02.PrimalItemArtifact_02'" 1 0 0
Artifact of the Massive -
giveitem "Blueprint'/Game/PrimalEarth/CoreBlueprints/Items/Artifacts/PrimalItemArtifact_03.PrimalItemArtifact_03'" 1 0 0
Artifact of the Clever -
giveitem "Blueprint'/Game/PrimalEarth/CoreBlueprints/Items/Artifacts/PrimalItemArtifact_05.PrimalItemArtifact_05'" 1 0 0
Artifact of the Devourer -
giveitem "Blueprint'/Game/PrimalEarth/CoreBlueprints/Items/Artifacts/PrimalItemArtifact_07.PrimalItemArtifact_07'" 1 0 0
Artifact of the Brute -
giveitem "Blueprint'/Game/PrimalEarth/CoreBlueprints/Items/Artifacts/PrimalItemArtifact_12.PrimalItemArtifact_12'" 1 0 0
Now once you have all 6, press Y on the terminal. You have to click on each artifact on the left, then move the cursor to the right to transfer it. Do this for all 6.
Once you've done this, the Green Engram should highlight. Select it, and press Y to craft it. With slomo up, this will go faster. You will now be teleported to the Guardians.
Now, enter the fly command. Fly around the map to the giant ape and the giant spider. Look at each one and type:
Again, targeting on slomo 7 might be hard, so drop it down. Kill both of these... and this is finally done!!!
It didn't pop the first time for me, maybe because I already had artifacts from before the update, but popped straight away the second time.
IT FINALLY WORKS!!!