End of adventure plot hooks

I am almost done with my Tomb of Annihilation campaign and am working together with my players to decide what to run next. The choices are:

• Continue with other Chult content.

• Continue with Vecna.

• Continue with another level 1-10 campaign involving one of the supporting antagonists (aside from Ace) in Vecna and then combine the surviving PCs from this and that one for a Marvel-style team-up against Vecna after that.

I have prepared plot hooks for all three.

• Plot Hook for Vecna:

  • If the PCs beat Acererak, he says "Fools! I did not merely wish to keep the souls of this world for myself! I only wanted to keep them out of the hands... of Vecna. You have no clue what lies ahead."

• Plot Hook for More Chult Content:

  • A multi-sided war wages above ground in Omu, which the PCs are experiencing during short rests through the eyes of Sewn Sister clones tasked with stirring up a bloodbath. Two factions of Yuan-ti, vs. Kobolds, vs. Grung, vs. the Order of the Gauntlet. The goal is to cause enough death to hasten the Atropal to full godhood. The PCs have been able to make contested wisdom or charisma rolls to gain control over their clones, or at least guide them in the right action.

  • When the surviving PCs make it to the surface, they have done everything right. Ras Nsi is defeated, the alliance of the Order of the Gauntlet and Grung controls the ruins of Omu... then Thayan airships darken the skies and Valindra steps out of a portal, saying that Thay is claiming the ruins of Omu for themselves, and if the PCs and their allies know what's good for them they will depart without protest.

• Plot Hook for Level 1-10 Campaign, followed by Vecna:

  • Upon returning to Port Nyanzaru, Syndra Silvane tells the survivors that the Harpers are aware of the threat of Vecna, and that as this threat is an inter-dimensional threat, it requires things to turn out right elsewhere in the multiverse. She then gives the following hooks:

  • Shadow of the Dragon Queen: Tiamat (I am putting her Forgotten Realms arc in the backstory because I have no intention of running it) has launched a full-scale invasion of another world.

  • Curse of Strahd: A series of mysterious disappearances afflicts the Sword Coast, and the Harpers suspect people are being whisked away to the Demiplane of Dread.

  • Syndra and her contacts can help any surviving PCs reach those locations but it will have unforeseen consequences (read: they will be de-leveled). Players can then choose to de-level and carry over their ToA PCs or make new characters while leaving their ToA PCs to prepare for the confrontation with Vecna.

Any thought on this or suggestions on how to improve it?