Plus, the Ordo Xenos would finally be on the same footing as Hereticus and Malleus, rather than being the neglected 'also ran' branch of the Inquisition, as they are in Calixis
Really now? I run a Xeno campaign, and I was never short of things to get going with, from Orks in a Space Hulk to the aftermath of a Dark Eldar raid (and following operation to get some eldar 'hard drive' left in thier destroyed psychic jammer) followed by a rogue Rogue Trader who wants to make a coup d'état to have his own planet in the sector to hide his illegal loot by controlling the feral orks population into a frenzy thanks to his freeboota hirelings, to a mysterious vigilante equipped with Jokaero technology waging a one man war against the Beast House and the Kasballica.
Also to me, the Beast House is really a Xeno opponent, and the Kasballica is a good overtly covert organisation that has a good deal of cloak and daggerry to it.
not as flashy as daemons walking out of a warp portal nor as action filled as raiding a cultist base during some dark ritual, but Xeno got all the nice toys.