Is a "mercenary copilot" able to change one hit into crit when he fires a "heavy laser cannon"? I would guess "yes" because of the word "immediately". Any FAQs about this somewhere?

Heavy laser cannon:

"Immediately after rolling your attack dice, you must change all of yourcrit results to hit results."

Mercenary copilot:

"When attacking at Range 3, you may change 1 of your hit results to a crit result."

Thanks

Yep. You turn all naturally rolled crits into hits (hence the word immediately) and then can turn hit into a crit. When you reroll dice via TL or predator, you also get to keep the crits. Part of the reason it's 7 pts.