Last week Games Workshop announced Warhammer Adventures - fiction set in the Warhammer settings for young readers (8 to 12 years of age). So, not teens, but preteens.
Warhammer, whether fantasy or sci-fantasy (40k) is a dark and dangerous setting. Tweaking it for the 8-12 y/o range is going to require ignoring much of the lore.
I’m sure it will be hugely marketable based on the “Warhammer” name alone.
Ah well,time will tell. The two Warhammer Adventures lines release in 2019.