@40kponyguy
 
@BackgroundLoL  
Also, Sisters of Battle also have some similarities to Emperor’s Children and Blood Angels. Adepta Sororitas, are after all, also known as “Daughters of the Emperor”, and Sisters of Battle are alsso obsesed with perfection, although spritual perfection/purity, but that’s fairly close to what Emperor’s Children and Blood Angels do, if a bit different, and also similar to World Bearers. But also let’s compare the The Flawless Host , which is also obsessed with purity (and originally, The Flawless Host, were an offshoot of the Emperor’s Children). There is also a reason why the most famous Sister fallen to Chaos, Miriael Sabathiel fallen to Slaanesh…
 
About Blood Angels connection, some think the Sanguinor, was a prototype, for the Living Saints, conciously, or sub-conciously made by the Emperor (or Malal…).

@40kponyguy  
Well yes it’s a great fit’s, although Rarity is capable of self sacrifice, and great amounts of generosity, which could also make her fit into Blood Angels, who also are perfectionists, and are artistic. Others also proposed Ultramarines for Rarity. It is interesting though that Blood Angels are compared at times to the Emperor’s Children, them miroring each other in many ways, and I saw Heresy AUs, were the Blood Angels and Sanguinius, or Ultramarines and Guilman fallen under Slaanesh:  
The Roboutian Heresy (Slaaneshi Blood Angels)  
If the Loyalist Primarchs were the Traitors, what would happen? (Warhammer 40k/Horus Heresy Theory) by Tactica Imperialis (Slaaneshi Ultramarines)  
What If The Sides Of The Horus Heresy Were Swapped? - 40K Theories (Slaaneshi Blood Angels)  
(Ultramarines actually do make sese, from their perfectionism standpoint. This is visible in the latter circles of Slaanesh’s palace - the Fourth circle - the circle of Paramountcy, where the traveller is greeted by roars of adulation, and is tempted with absolute power over others; 5th circle, the circle of Vainglory, were traveller is presented with his ideal self-image, and if he feels but an ounce of pride, for eternity will this circle be his prison. The 6th circle heavenly place, within which resides a seemingly perfect environment. All of this I think fit as temptations for Guilman and Ultramarines).
 
Also, about Rarity and Emperor’s Children, Rarity as Fulgrim:  

I still think Rarity fits better with the Emperor’s Children myself.
 
Always trying to better themselves.
 
The Vanity is strong with this one.
 
And finally, 30k. Base colour? Purple, White and Gold.
 
That said, this isn’t badly done, and we’re overdue for some fresh crossover art.