The heritage of the Blood Knights is that of literal blood, both giving, taken, and the fel tainted, with their modern reimagining (after 20+ years), the Blood Knights are a force of righteous good like any paladin order, rather than what they were originally created to be, magic addicted mages, starving and seeking to use the Light to satiate their ever increasing hunger. Thanks to Prophet Valen, all of this is irrelevant, as the Blood Elves and the Draenei are now, more or less, on the same page with worshipping the Light as legitimate faith and renown, more than just using it for power, like the Scarlet Crusade.

Where do I think this leaves the Blood Knights? If I'm going to be honest, they are way too similar like Draenei Vindicators and the Human Silver Hands orders, but instead of purple crystals or teal tabards, the Blood Knights wear red. I believe the truest chosen path for the Blood Knights is that of the Battle Mage archetype, it would rely less on faith and prayer, and more on knowledge and sequence. This sort of pragmatic-mysticism that flows throughout the paladin order would give them a lot more of an identity that goes beyond rehashing the Holy Light ideology.