Don't forget R5-X3 for Asty, they were made for each other (and he's cheap as chips).
Considering the value of the astromech slot, R5-X3 should've been free. A free droid with a free integrated astro would've been a good boost for an X-wing just looking for the extra hit. And considering it isunique, one-use-only, and using R5-X3 also effectively cancels IA, it wouldn't be game breaking at all.