What follows is a list of all upgrades that only appear once, in ships that you can only be fielded four-of or fewer in a 100 point fleet.
The number to their right is the difference between the max number their ship can be fielded in a 100 point fleet, and the max number the upgrade in question can be fielded in a 100 point fleet. Upgrades with negative numbers have been removed.
Which of them do you think needs to be re-released, as Push the Limit once was?
R5 Astromech 1
Countermeasures 1
Tactical Jammer 1
R7 Astromech 2
Navigator 2
Tactician 2
Expose 2
Predator 2
Ruthlessness 2
Engine Upgrade 3
Stealth Device 3