So just to make sure I'm reasoning this right, and that I couldn't find another thread on this specific thought...

If Keyan Farlander has Opportunist, does this mean he can:

1) Roll weapon attack dice and declare Opportunist is being used (by meeting card requirements) for extra die + stress token

2) Modify roll by spending stress token to change Focus results to Hit results

These both fall under Modify Attack Roll in my mind so they would resolve in that order.

Also, we've agreed (I believe) that Opportunist works on secondary weapons, but does Keyan's card ability work that way too? If so, with HLC + Opportunist + Jan, you could in theory roll 6 dice with all Focus being changed to Hit by spending the Opportunist Stress if I'm reasoning this correctly.

Right?

These both fall under Modify Attack Roll in my mind so they would resolve in that order.

Since you get to decide the order things like this happen in, I think you're right. You'd use Opportunist to gain a stress token, which you could then spend using Keyan's ability.

but does Keyan's card ability work that way too?

Yes, unless it says Primary or Secondary weapon, then the ability effects all attacks by that ship.

If Keyan Farlander has Opportunist, does this mean he can:

1) Roll weapon attack dice and declare Opportunist is being used (by meeting card requirements) for extra die + stress token

2) Modify roll by spending stress token to change Focus results to Hit results

Yes he can. Note: You declare opportunist before rolling dice. Not after.

These both fall under Modify Attack Roll in my mind ...

His ability happens during modify attack dice. Opportunist has to happen before/during "roll attack dice".

Also, we've agreed (I believe) that Opportunist works on secondary weapons, but does Keyan's card ability work that way too? If so, with HLC + Opportunist + Jan, you could in theory roll 6 dice with all Focus being changed to Hit by spending the Opportunist Stress if I'm reasoning this correctly.

Correct.

dvor has it.

I've actually used this trick with Ibby, who gets much the same effect - use Opportunist to boost the attack, and then immediately leverage the stress. Of course, Farlander does it better, but he does pretty much everything better at this point.