I too intend to award a certain number of picks per mission (based on the NG guideline, with 1 pick = 200 XP).
For the problem of players maxing stats too quickly, I was considering the house rule of adding a time factor to raise a skill/stat. I used something similar in ICON, considering that a character needs some hours training per day to be able to spend points in a skill.
Something like Current level times Picks cost in days appeared OK to me (considering at least two hours per day are spent practicing the skill). That may slow down the maxing of professional skills.
"The main difference between Trekkies and Manchester United fans is that Trekkies never trashed a train carriage. So why are the Trekkies the social outcasts?"
Terry Pratchett