Trebs are not particularly useful against bombers, I'd rather have a maxim by far.
As for uses of the Serapis...
Scrap metal?
Horrible fighter, Horrible.
Sucks as Space Superiority unless you're talking about 1on1 TvT and you already vastly outskill your opponent (it's light enough that you'll never get touched, unless they take a loki).
Sucks as Intercept unless you blitz in and out before the bombers can turn on you (...doesn't happen on insane, just doesn't).
Sucks as Assault period.
It has one useless primary bank and one useless secondary bank, useless shields, slower than the ship it's replacing.
The ONLY thing it has going for it IS the maxim.
Well, and that awesome primary bank, but still, I'd rather fly pretty much any other ship in the Vasudan Armada.
..And that's saying something since almost all the badly designed ships are Vasudan.
They have one decent bomber, and their fighters are intensely situational with very little overlap.
And they're all stupidly big when it comes to target profile in dogfights :<
/Rant
So yea, Advanced Interceptor, because it really can't do anything else.