I think timegate-ing progression is somewhat backwards in this situation. The event is not particularly exciting to begin with. Furthermore, let's think about what would happen if they did timegate it. Then they have to have a specific time at which this new event would take place, likely during a weekly reset. People who can't make this time wouldn't be able to see the progression anyways. Furthermore, it doesn't incentivize playing when the bar is capped, which would drive down engagement. All of the interesting gameplay is through the quests which are available all the time, the mech missions, which happen at 20min intervals and the red alerts, which happen once every 4-8 hours as I understand it.
Alternatively, you could make the event quests available as a solo instance, but again, I'm not sure most people would willingly go and do one since it's just running back and forth.