If Custodes are they're own damned book, Kroot ought to be one too. Every time I see them golden boys, I say "if they're here.... WHO'S GUARDING THE EMPEROR?!!?"
Back when I played fish'ead, I painted my hoofed warriors in bloody scarlet, at first I called it "commie red" but then when I got to my kroot I realized they were kind of like Redcoats- thin red line and all that. I painted my kroot a bit like like Iroquois or Huron warriors. At the very least, I thought of the relationship between the two as being similar. IDK what they'd do with a krootdex though. Honestly I don't see a strong demand even from someone like me who actually liked taking the damn things.