If you want to do alternating activations the first thing you have to do is aggressively cut the turn down. Four 'phases' with sub-phases and reactions in some phases leading to units potentially doing eight things a turn (move, cast power, shoot, charge, fight, deny power, overwatch, fight again) just means you're going to need to spend so much time passing priority and figuring out order of activations that the game is never going to finish; most real alternating-activation games (Bolt Action, Legion, Xwing, Crisis Protocol, etc.) let units do about two things a turn.
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