I personally do not think Yoda or Obi-wan have any place in X-wing. There is a better argument for Ob-wan than there is Yoda, but there have been two Falcon sets now and I don't see him as being anything other than a crew for the Falcon.
In a way, Obi-wan IS in the game. Deadeye feels like Obi-wan helping Luke guide the torpedo without a target lock. The T-65 X-wing also came with Marksmanship (a similar effect as what Obi-wan helps Luke do while flying a starfighter).
But if they did make an Obi-wan crew card it should be as follows:
Obi-wan
Rebel only - Crew
0 points
When Obi-wan is needed most, flip this card face-down and tell yourself to "use the force" instead.
Why not?
If it's because they're dead, half the pilots or crew in the game are dead. Many of them before the OT (e.g. inquisitor).
If it's because they're not shown prominently flying or crewing starships in the OT, then FFG should've stopped publishing new material waves ago as half of the current pilots (e.g. all of the bounty hunters except Boba did nothing more than stand and grunt for 30 seconds in Empire).
If you take into account their activity in the clone wars and/or the Legends EU (both of which have led to many other pilots and crew being in the game) there is plenty of justification.