I'm going to be a little unorthodox with the thingie and kit it with only one Aux2Bat (experience has taught me that A2B is pretty good on science as well, since it lets you either reduce the boff weight needed, or diversify; all you need to worry about is timing), and complement of full smorgasbord of all sorts of goodies besides (such as Photonic Officer II). 3/3 is standard for pure Carriers and Sciboats, but the Breen Carrier has 4 Tac consoles which is p. sweet and its boff layout is still better than its closest competitor Kar'fi.
But yea, generally speaking you only need Cmdr Sci, anything besides is ultimately excess. The ideal pure Carrier would have Cmdr Sci, LtC Eng, LtC Tac, Lt Eng, and a Universal something something.
My current plan in terms of abilities:
Tac Team (partially doffed), Attack Pattern Beta I, Fire At Will III
Polarize Hull I, Hazard Emitters II
Science Team I/Transfer Shield Strength I/, Tractor Beam Repulsors I, Photonic Officer II, Gravity Well III
EptSI, Aux2Bat
EptWI, RSP
Twin hangar cooldown doffs, broadside of Antiprotons (it's a kitty, I don't have to give a fuck), and the standard set of gear.