u/JagexFrosch Ditto to Giveme's comment above. I've already left survey feedback, but rereleasing the same Challenger Halo would be boring and is a sure way to reduce the likelihood of people wanting to compete/participate in FSW again. Part of the excitement was due to the novelty/exclusivity of these items, so I'd strongly suggest the development team consider brand new items and abilities (I'm sure the survey data will also be informative).
I would suggest a new Challenger item, a Challenger amulet/necklace/pendant, and perhaps an entirely new item that can be earned. I think it would be fine to reintroduce the same skilling capes, and inverted master capes, and pets. I would also suggest a new version of the skilling pets, and perhaps just make the chances of unlocking the old halo pets based on chance.
Maybe, the new item replacing the Halo of Returning could be the Black Partyhat? The Halo of Returning was a cool homeage to the Disk of Returning. Introducing a new Black Partyhat as an item that requires 8 shards, and marketing it as one of the prizes will absolutely increase the amount of activity, and desire for players to participate in FSW in the future.
I don't want to highjack this reddit thread, but I think it would be great if Jagex could possibly start a thread on the Runescape Official Forums to collect feedback from players and incorporate them in the conversation when they're looking to reimplement FSW (or something similar) in the future.