Ok, here's what you do.
Log on on tribble, take the Excelsior out of mothballs, or the Sovereign refit if you want to go 24th century, fit her out with either Quantum (180° arc if you have it) or transphasic breen rapid fire torpedos.
Two launchers front and rear.
The rest phaser turrets.
Then you train your tactical officers torpedo skills.
Get those doffs that reduce your torpedo fire cooldown to an absolute minimum.
Reduce weapon power to a minimum, torpedos don't need it and the turrets fire at a high enough rate and proc relatively often to shut down subsystems.
Put enough power into the engines to get a good turn rate and the rest into a balance of shields and aux depending on how important your sci powers are to you and how much shields you need for survivability.
Respec and max out your torpedo/kinetic weapons, targeting skills, evasive and defense, you don't need a single point in energy weapons anymore.
Get a tractor beam or two, maybe a tachyon beam if you have the room.
Engineering should be standard defense, power to shields and engines, aux to structural integrity and a good offense power: warp plasma to shake of all the stubborn escorts in your rear.
Experiment with the fine tuning of this build.
Once your satisfied, copy the build on holodeck and have fun in pvp with a cruiser.
All careers should do well here. Engineers can survive the longest under heavy fire which is important with a torpedo build, as it's not a spike damage build, but deals steady heavy damage over time. Balance between shields, engines and aux should do well.
Tacticals max out the damage you will do. you have two arcs you can do heavy damage from. Thanks to the warp plasma, you might even be a little better from your rear arc which negates the disadvantage of your turn rate. High power to engines is a must.
Science can mess with other players systems and distract with holofleet and stuff. High power to aux to maximize your science captain powers.
This build should also work exceptionally well in a science ship like the Vesta or Intrepid which feels cruiser like enough. The Nebula might also be a very very good choice if you want that cruiser feeling but have more science power.
This build will not be a fast killer like the best escorts, but you will consistently score high, be competitive and contribute in a meaningful way.
Maybe get a refit console that compliments your build for an additional power.
my starting thought behind it is this: While everyone moans about killer cannons and escort zippy flying being mandatory and beams sucking to no end many people forget torpedos as a very canon weapon.
my inspiration for it was the final battle between General Chang and Kirk/Sulu. No one fired a single phaser shot in that scene. It was all torpedos.
Sure they lose massive damage against a sliver of shields, but they STILL deal impressive damage over time. Quantums by virtue of having the highest non-heavy torp damage and fast travel rate and transphasics by having a high bleed through (and if you don't care about the name they still look photon torpedo like enough).