Breakpoint needs an enemy Reinforcement Mechanism - as clearing certain bases are a walk in the park going in guns blazing.
The only time the Trailer is Accurate in Difficulty is if you are trying to Role Play as a Spec Ops Operator.

Otherwise, you really don't need much coordination or thinking involved.


Radio Room \ Radio Tower \ Recon Radio Operator \ Base Commander

To make the reinforcement mechanism work needs 4 things.

Radio room
is essentially a room in each Outpost \ Base \ Building Complex, that allows any enemy unit ( the game assigns nearest one randomly ) to rush to the room to call for backup when status is alerted. That means the first priority for the operator is to locate the enemy radio room and shut it down.

Again just because the Radio room is "Shut down" does not mean the enemy should ignore it. The enemy still needs to go to the Radio room and "Confirm" it has been disabled by having chatter on the radio, "We have been sabotaged the radio is out!" or "Someone destroyed our Coms! "

( Again a Good example of Ai handling this is Metal Gear Solid Phantom Pain )


Radio Tower
The radio tower is a larger structure unlike the Radio room requires explosives to disable ( C4 \ RL )
The Radio tower once destroyed alerts the entire base.

Which results in Communication,
"Some one took out the Tower! Some one alert the FoB!" - If Commander is Dead
"This is Base Commander Orion - We are currently under attack and coms are down. Initiate Protocol Romero Echo Delta. I want this Ghost Dead" - If Base Commander is Alive before Alert Status

This results in one enemy nearest to a vehicle to take it and travel to the nearest forward operating base to call for backup.
This allows for more tactical play.

If the user already attacked the nearby FoB ( The Refresh cycle needs to changed for repopulation to only once every 24 in-game hours for this to work )
Backup will never come as the base was already destroyed.

This could be taken a step further by having the FoB - be Procedurally placed in various locations. Then having the player hunt it down by interrogating wandering patrols.
This allows for "Dynamic Intel" generations. As patrols near the area will be aware of the FoB \ Base Commander Location \ Radio Operator )..

For Base Commander Location - you only learn of the "last Known location of base commander" they have a larger patrol route and different routes in day and night.


Recon Radio Operator
These Guys patrol around the Base and Some times walk back into base to switch duties. If the base goes on Status Alert or Red Alert they return from their patrol route back to base to call for reinforcements.

Players can hunt down patrols and interrogate them to find last known location of the Radio Operator. ( Again adding more Dynamic Intel )

Base Commander \ Officer
These guys decide the type of Ai you will be facing.
If the Base Commander is Alive the Ai is smarter - enemies will buddy up in teams of 2 - 3 and take different routes toward the last known location.
While Mortar will shoot multiple shots randomly ( not with god-like precision - but with more shots fired to make up for it ) Around last known location.
The Mortar will avoid trying to hit units in its own faction. Instead will focus on bombing potential escape routes.

If Base Commander is dead. Enemies will not group up but randomly wander around looking for the enemy. Only a few peeling off to last known location.
The Mortar will not care if "Friendly" units are nearby and can accidentally hit it's own team.

Reinforcements

There are 3 possible Reinforcements.

The first level of Reinforcements comes from the nearest FoB

Reinforcements can also come from Wandering Patrols ( Troop Convey Trucks ) that pass the area when an area is alerted.
A truck should pass by each area every 5 - 10 minutes. Allowing players a more tactical approach by waiting for the truck to leave then attack as they know a window has opened up.

( Currently - if the base is under attack the Convey truck literally just drives by pretending nothing is wrong!!1! )

On Alert Status 2 - if a comms officer is still alive, or they managed to get communications out somehow.
Commander Alive on Stage 2: "This is Base Commander Orion - We are Under attack, I repeat Heavy attack, we have Suffered Heavy Casualties. We need backup ASAP"
Commander Dead at Stage 2: "This is the Coms Officer, our Commander is down. I Repeat our Commander is Down. We need support and we need it now"

If the Commander is dead at Stage 2 Alert - a Bigger wave of reinforcements comes than if the Commander was alive. Since it means they are in a worse off situation.
This allows the player to decide whether to keep the Commander alive or not. The player could even capture the commander and force him to call off the reinforcements, which could result in a 30 \ 30 \ 30 Dice Roll.

1. He could comply
2. He could refuse
3. He could alert Central Command to send everything they got before being killed.

At this point Spawning from the Nearest Primary Base an APC filled with troops will travel down the road to the base. If the Base is in a Remote area then 2 Blackhawks spawn at the nearest Base with a Helipad and come toward the base.

The players are alerted by their locations on the minimap ( similar to Drone \ Helicopter alert )

Which means players need to finish their objective in that area and leave before reinforcements arrive. Or be ready for a heavy firefight.

Such a Deep Mechanism will make players feel they are being hunted, need to think carefully before approaching an area. Will require multiple levels of interaction with each base to plan for contingencies Adding a lot more life to the game. .