Please correct me if I misunderstand this, but it seems to me that you can take allies without using the Allied Detachment in the rulebook.
Is that correct?
Mostly looking at Craftworld Eldar and Harlequins, but I understand some of the new Mechanicus codices don't have HQ's either.
You would just have to use the Harlequin detachment if building a Battle-Forged list, right?