The failed engagement roll meant that the plan type didn't work as intended and the PCs lost the initiative. So, I described some events that resulted in that outcome, using my understanding of the situation on the ship.
There were major repairs taking place, so I thought, "What if one of the repair jobs suddenly goes haywire, right when they try to launch their deception?" This is also in keeping with the idea that a bad engagement roll isn't necessarily the PC's 'fault' -- it's just bad fortune.
Since the ship probably has an alarm, and the marine squad probably wasn't birthed on board during repairs, I made a 'reinforcements' clock to count down to their response to the problem. For the marines themselves, I assumed one squad on-call and the rest on shore leave -- so a small gang (5 people) with Tier IV gear and combat training. That means ZERO effect for the PCs in a fight with them, by the way. (They'd need to push themselves and attempt setup actions to hurt the marines at all.)
Anyway, in short, first I decided that things went bad because of the failed engagement roll. Then I looked around at the fiction and made clocks to reflect what I saw.
He did it to be a badass. And it worked out.
Aldo's roll against Master Chauk. It was desperate, so Aldo was risking severe harm (level 3) as the base, +1 because Chauk is a higher-Tier badass. So that's fatal harm at risk.
Carriless walks through the fire. Risky roll, so Carriless is risking standard harm (level 2) as the base, +1 because of the potency (it's metal-melting electroplasmic fire). So that's incapacitating harm at risk.
Carriless fights Clave. She's a master sword-fighter, desperate roll, so that's severe harm at risk (level 3), +1 because of her higher-Tier finely crafted weapon. Fatal harm at risk.
Rune channels the city power grid. Obviously, fatal harm at risk.
They rolled sixes, so they avoided those consequences. Even with 5s, they would have suffered all of the above. I'm not pulling any punches.