I gave the technician's floatie-talkie to Marcus, opened the Arch Keep and joined the pirates just before talking with Chief Briggs about failed Cruzer's attack, but didn't accept any of the Captain Grim tasks (did one for Razor, though, and learned naval combat), and returned back to complete the remaining quests for Aegis. The jet was stolen without anyone noticing, but Aegis became suspicious and refuse to reply via NavCom, though are still friendly if meet in person. After completing all their quests, the Expedition leaves and there are no jet ski patrols anymore; but if speak to Grim again he will claim there still are, and give task to hunt down Aegis, which can't be completed.
If provoke Expedition before they leave by accepting Grim task to kill the patrols, dead Cruzer dialogs will be present in further pirate quests, he'll be labeled as "Unknown".