For a big game I'd take a city and do a modern revolution scenario. There'd be an authoritarian military police force with armoured vehicles and checkpoints and like Adolf suggested all civilians would have eye pro and chronos. A phone app would give each player locations of objectives and friendly forces as well as requests for help and other intel.
All security players have regular patrols and FOBs that they can rearm and respawn from. The resistance players have safehouses and from there can launch guerilla attacks, blending in with civilians to get close and break contact. They also get access to satchel charges, IEDs and car bombs whereas the security forces only get smoke and "tear gas" grenades to reduce civilian casualties.
There are no medics. If you go down your team has to retrieve you and get you back to a safehouse or FOB. If you go down the other team has the opportunity to capture you and bring you to a base where they interrogate you and gain a piece of intel which is given by the app. When a side has enough intel they can attack a base and free any teammates held there. At the end of the event the team with the most intel will attack the other teams main base in a final climactic battle.