RULES UPDATE: Future Fusion!

Internet archeological forum activity points to a discrepancy in rulings surrounding one of the most powerful cards in the format - "Future Fusion". Special thanks to MMF for bringing this to the community's attention and providing a timeline of events regarding these changes!

the TL;DR (click "Read More" for the revised rulings):
- You CANNOT activate "Future Fusion" while "Vanity's Fiend" prevents Special Summoning.
- You CANNOT activate "Future Fusion" while a "Barrier Statue" monster is face-up UNLESS the Fusion Monster you intend to reveal has the allowed Attribute.
- You cannot reveal "Five-Headed Dragon" while "Koa'ki Meiru Drago" is face-up because it is DARK.

Future Fusion
(1) Send, from your Deck to the Graveyard, Fusion Material Monsters that are listed on a Fusion Monster Card, and select that 1 Fusion Monster from your Fusion Deck. (L) Special Summon a Fusion Monster from your Fusion Deck with the same name as the selected Fusion Monster during your 2nd Standby Phase after this card's activation. (This Special Summon is treated as a Fusion Summon.) (2) When this card is removed from the field, destroy that monster. (3) When the monster is destroyed, destroy this card.

• "Future Fusion" must remain on the field for any portion of its (1) / (L) effect to resolve.
• The (1) effect activates when the card is played face-up on the field. If it resolves, it creates a Lingering Effect (L).
  • There is no cost. The Fusion Monster is revealed and the Fusion Material Monsters are sent to the Graveyard at resolution.
    • Only correct Fusion Material Monsters may be used. Substitutes (ex: "King of the Swamp") CANNOT be used.
  • The (L) Lingering Effect applies during your second Standby Phase without starting a chain.
  • This card CAN be activated while "Dimension Fissure" is active. The sent monsters are removed from play instead.
  • This card CANNOT be activated while "Dimension Fortress Weapon" is face-up on the field.
  • If "Future Fusion's" activation successfully resolves: it is treated as having performed a Special Summon (in the future)
  • This card CANNOT be activated while "Vanity's Fiend", "Archlord Kristya", or "Fossil Dyna Pachycephalo" is face-up on the field (as these cards prevent players from activating cards which WOULD perform a Special Summon).
  • This card CANNOT be activated UNLESS the revealed Fusion Monster's Attribute is permitted to be Special Summon while a "Barrier Statue" monster (or "Koa'ki Meiru Drago") is face-up on the field and applying its Continuous Effect.
  • This card CANNOT reveal a Fusion Monster whose Fusion Material include at least one Fusion or Synchro Monster.
  • This card CANNOT reveal a Fusion Monster whose Special Summon Condition restricts it to a specific Summoning procedure written in its text (ex: "Gladiator Beast Heraklinos", "XYZ-Dragon Cannon", or "Elemental Hero Grand Neos").
• The (2) Continuous-like Effect destroys the Fusion Monster immediately without starting a chain.
  • This effect no longer affects the Fusion Monster if it ceases to be face-up on the field (by "Book of Moon" or "Interdimensional Matter Transporter").
• The (3) Continuous-like Effect destroys "Future Fusion" instantly without starting a chain.
  • This does not occur if the Fusion Monster leaves the field without being destroyed (by "Compulsory Evacuation Device").
    • "Future Fusion" will continue to occupy a Spell Card Zone without effect.