It's a bit fuzzy but . . .
Specialists will use one Slot for their choice of 'normal' Gadgets geared towards their specialty .
To upgrade that Slots Gadget , they'll Call-in for some Commander-provided higher-end stuff .
Before their Call-in , the Slot had (for example) a low-yield explosives-laden anti-Vehicle 'Dog' .
After the Call-in , there's now a nasty Rocket-equipped bigger-than-RAWR mini-tank in the Slot .
Before , a spy MAV with EMP firepower .
After , a spy Drone with missile-firepower .
As Call-in upgrades appear to Commanders , so too does the list of who Called-in appear .
With a quick glance at the scoreboard , they decide who is most worthy of wielding 'Mjolnir' .
If this isn't fuzzy then . . .
Specialists will require Specialists to Counter them .
I like the series' track record in the game of Countering .
There's an amazing war on the horizon .