kietotheworld: No - destroying a capship in subspace would be suicide - the node would collapse, and you'd be destroyed along with it. Ship-to-ship combat is a big no-no in subspace. Besides, it'd be almost impossible to get into a position to launch an attack, and even less likely that the attack would be under favourable conditions - just getting into a position where you could follow the Lucifer into subspace would be very difficult.
The idea of beam weapons was copied from the Lucifer's superlasers by the GTI AFAIK - it's likely that the GTD Hades would have carried some form of beam cannon had it been completed, making it vastly more powerful. The shocking performance of Alliance capital ships against their Shivan counterparts was one of the biggest problems that needed to be urgently addressed after the Great War - the lack of useful ship-to-ship weaponry was the main problem, with Terran and Vasudan turrets being far inferior to the Shivan turrets. And the power of the Lucifer would have been terrifying - a ship that destroyed the GTD Galatea (one of the most famous and valued ships in the entire GTA) in a matter of minutes, with only a few volleys from it's main weapons. FS1-era Alliance ships didn't have anything like that kind of firepower - it'd be like having a 16th-century galleon going up against a 1930's battleship.
Beam weapons were developed to counter the Shivans, but I suspect that the GTVA was dreading the possibility of another Lucifer - hence the Colossus, which was the "secret weapon" to be used if another Lucifer fleet appeared...
