I had a similar problem with a Tac and wanted to pilot a Gorn ship.
I thought have cannons at first but decided against them after trying them out. As a Sci ship the Varanus gets 4 of the target sub system abilities. Two of those aren't the best, but targets weapons and shields are extremely useful, and they are free powers on a ship that only has two tac boff slots.
This character will hit Rep 5 tomorrow and I think I'm going to get him the Omega plasma torpedo and cutting beam, they will probably be useful in this setup. I haven't parsed with the current config, but I can tell you its putting out alot of DPS, 1,100dps from the each of the dual beam banks alone, unbuffed. Buffed they are well over 2k.
I've also chained the target subsystems and torpedo spread together so this ship always has at least one of those active.
Anyway, here it is. There's still room for improvement though. All the weapons will eventually be replace with fleet variants. I do have alot of shield and hull heals. The hull heals might be alittle redundant with the repair platform and might try out some powers once I get around to it.