The Destiny Ascension absolutely sucks in the battle against the Sovereign and the Geth because they come in at close range, and traditional space battles occur at dozens, hundreds, or thousands of kilometers range. Therefore, I think her most powerful armaments are all linear firing mass accelerators, probably requiring the whole ship to turn. Thus I'd strike those out, unless its possible to script a torpedo that fires at thousands or millions kph and with like a 1 degree firing arc.
I'd probably deck the ship with point-defense lasers on every surface, maybe half a dozen spaced around each arm. It's unknown whether Javelin disruptor torpedoes are unique to humans only or not, but the concept (miniature mass effect cores used to disrupt the space an enemy vessel occupies upon impact) seems sound enough and something I would have thought up if I had space-warping material. You could probably get away with similar weaponry. They are fired in the "knife-fight" range because they don't move at relativistic speeds and must be fired close so as not to be intercepted by point-defense weaponry or by kinetic barriers.
