I've been going with the minimal upgrade approach for now, opting to trade the upgrades for a Tie Fighter like Backstabber in its place.
My favorite setup so far is:
Captain Oicunn
+ Darth Vader
It is simple, free damage, in multiple forms. You don't feel TOO bad when you Vader, since only 45 pts. Also, creates funny dynamics where your opponent's high PS ships will have a hard time choosing to fly passed the Decimator and get a Vader crit (after being rammed on my move, of course), or choosing to get rammed on the next turn by picking a dial choice that will bump the Captain, if that makes any sense.
With supporting roles such as:
Whisper + Vi + ACD + FCS
Backstabber
or
Howlrunner
3 x Academy Ties
I tried kitting out the Rear Admiral and Kenkirk, but didn't like the support options all that much. It came down to me trying to win with my turreted ship, which wasn't any more fun than flying a Falcon. I think any kitted out Decimator I run will be supported by 2 x Shuttles + FCS (46pts), so the Decimator will be under 54 pts. Can still fit some good stuff in that. Any more and you are stuck with 3 x Ties, 1 x Phantom, 2 x PS1 Ints. Maybe...Engine upgrade on a turret ALWAYS changes my mind.