A good GM can already sort of simulate that, but how do we SUPPORT that? With play cycles. The first element is "Hotspots". These are obvious. These are your XCOM2 mission targets. Where these are marked, you have a guaranteed Tactical Objective. Mech fight or no, this is the familiar game.

So the players select a hotspot, they play through that sequence - maybe it's a one-off fight, maybe it's a staged setpiece, it varies, more on that shortly. And then you begin a new PHASE. Time ticks forward one unit, the players get some free actions, and then decide again.