The real question is timing windows during a player's turn. I know you can start your turn and have a window to play a Tactic Card before you activate someone, but is there also a window to play one after a character's activation is over but before your turn ends.
Also, could you play a card in-between actions during an activation. For example: Mystique attacks for first action. I play Juggernaut's throw card. Mystique attacks again for second action.