How the MCU could revive a major dead Avengers: Endgame character

Significant spoilers ahead for Avengers: Endgame and Agents of S.H.I.E.L.D.
Up until Avengers: Endgame, hero death in the Marvel Cinematic Universe was rarely permanent. Agent Phil Coulson died in The Avengers, and was resurrected for Agents of S.H.I.E.L.D. Bucky Barnes appeared to die in Captain America: The First Avenger, and came back as the antagonist in Captain America: The Winter Soldier. Even Loki, a villain turned semi-hero, seemingly died in Thor: The Dark World, came back for Thor: Ra