Some ideas for planets.
[ ] Weeest 2: A jungle planet populated by earth descended tailed primates ,enhanced by the Ancients during the Dark Age of Technology. The local Forge World is dominated by your fellow Genetors, and considers the local primates to be gifts from the Machine God. Rumors persist of a 'king' primate that was able to fight multiple greater daemons during the heresy.
With Adaptive and Thousand Suns we could legit get Psyker Monks maybe? Mystical Martial Artists sounds protecting ancient knowledge sounds awesome.
[ ] Sightless: The rather on the nose name of this planet is due to the fact that a large portion of the planet's population is blind - thanks to the local wildlife, whom seem to consider human eyeballs a delicacy. It a rare individual on the planet of Sightless that keeps one eye late into their lives, let alone both. (Ultramar Region)
Irony, So much ancient knowledge but no eyes to read it. Truly a curse for the Sons Of Magnus...
I was also considering Sightless as a pure joke choice. (The symbology of the sons of Magnus getting their eyes ripped out all the time is also neat, now that I'm thinking about it)
My favorite choices if we end up choosing the thousand sons would be:
[ ] Skaltland: A large planet of lush green forests, the inhabitants are tough and belligerent folk - being extremely prone to excessive swearing, and picking fights at the drop of the hat. And this is without the horrid shrieking caused by the 'bagpipes' that are their most popular musical instrument. (Fenris Region).
or
[ ] Dugronk: A Feudal World located near Skaltland, and with a very similar culture overall, the land of Dugronk is mostly swamp interspersed with medieval castles. Of note, several remarkably intelligent but somewhat surly Ogryn tribes call this planet home. You wonder if you could take a look at them, you
have been hoping to find a way to repair the genetic damage that leaves most Ogryn so simple minded... Bah, no time. (Fenris Region).
(I would explicitly choose Dugronk for the ogryns, but Skaltland is more overly Scottish, and Dugronk is also a swamp, which doesn't seem that good for storing knowledge, to be honest)
Placing the thousand sons right next to the space wolves is funny, and turning the Thousand Sons into crude, loud scotsmen while they are also, simultaneously scholars, seems like the correct amount of irony to me.
Also I would get to call it Plan: Thousand Scots