Can - a couple things:
First, when the heck would the Alliance have had the time to raise a generation specifically to send off to Sirius? That just seems dumb - if they raised a generation, it seems they would have been put to better use beating off the Coalition dudes.
Second, while I agree that ships should be more specialized in their roles, I don't agree that they should be in those rigid classes. There should be one more class of ship than we have (LF, HF, Interceptor, and Freighter), but the three fighter classes should be far more diverse. In my mind, we're looking at:
Interceptor - really light, fast, and weak. They sport fast firing weaponry (the 8.33 stuff, potentially going as hish as 10.0) that does very little damage. They should be allowed to use Cruise Disruptors, as well as having their base engine speed be high (maybe around 150, 300 on burn, and 500 on cruise). For this kind of ship, the best weapons would probably be like a Nomad Beam/Chaingun style thingy. They should take about 2-4 guns. These should have the ability to mount one missile launcher in addition to the CD. These would be of the Stalker or Eraser series, up to the Class 5 level of Eraser or Class 3 level of Stalker.
LF - About the same strength as current, and sporting the 4.00-5.88 brand of weaponry (although with the weapons weakened a bit - these should be able to compete with 2.00 weaponry damage-wise). These should move at about current ship speeds with the current ship maneuverability settings. These should be able to use CD's or a crappy variant of Torpedo (maybe Light Torpedo or something) doing around Starkiller damage for the best variant of Torp. Their best weapons should be sort of like the current Nomad Blasters, though a bit less damaging. These could also carry medium-yeild missiles, like Catapults and Sunstalkers.
HF - Huge, lumbering, and devastating. I would say in the realm of 6-10 guns, if not more. They should handle like aircraft carriers and move slower, around 50/100/200. They'll carry the heaviest missiles and Torpedoes as well, including Cannonballs and Sunslayers. However, I would suggest adding more weaponry, as those 3 aren't really powerful enough to justify use. HF Torpedos should do around 20k hull damage, with the biggest missiles doing around 6k. These should not be able to use the Stalker series of missile. Biggest guns should do somewhere near 2k hull, but fire at a 0.5 rate and require MASSIVE amounts of energy.
Basically, I'm looking for a few extremely defined types of fighter which would be good matches for each other. While a HF could kill an Interceptor in 2 shots, it would be nearly impossible to LAND those shots on such a quick, small target. If you did this, though, there would have to be some justification to the damage potential of a HF....like, destroyable bases and base destruction missions that would take an interceptor HOURS to complete pecking away with their little lasers. The bases should have the kind of HP that would make it impractical to attack with anything short of an HF.