I think a big reason they had swordbearers is that the sword was integral to the Crota's End raid. The wolf fugitives had scorch cannons which was used (although not integral) in Prison of Elders. I think they did these things to familiarize the player base with relics, as a large complaint of Vault of Glass is that many players weren't capable of using the Aegis, and we're either kicked from parties or not selected for raids in the first place. I think Bungie specifically said the invasions were an opportunity to familiarize players with the sword so that they wouldn't face that same problem. Therefore, if King's Fall uses a different relic, there will probably be a new patrol mechanic based around familiarizing the player base with this new relic.