I get this feeling that we're going to get Mags, not Fuse. Her punkish outfit in the video looks nice, a bit more elaborated than what Fuse is wearing, would definitely be a nice skin for Apex.
A theory: Being mad about the treaty that practically puts salvonians under Syndicate control and especially because this has also taken her life partner away from their cause for good, Mags (and her salvonian freedom fighters) bomb the hell out of Kings Canyon, with some hope that this will at least break the alliance. This ends up badly, apparently killing Fuse this time and leaving her heartbroken. The Syndicate offers to the salvonian warlord to keep the agreement, with the condition that Mags is caught and given to them. The warlord agrees and the Syndicate gets her, but they don't jail or execute her, to not stir the freedom fighters even more. Instead, they offer her a path to redemption by taking part in the Apex Games, playing in the place that she destroyed. Later, as Mags rises to fame, Syndicate reveals that Fuse is still alive, kept in one of their jails as guarantee and then they warn her that they will execute him if Mags leaves the Apex Games to return to Salvo. Her love for Fuse will make her behave as good as gold.
Her tactical could be drinking some alcohol then spitting flames or a Molotov cocktail. Her ultimate could be a fire grenade or falling bomb that explodes on impact, either trapping the enemies or protecting her squad inside a ring of fire.