You have to try and take in account how well developed the other systems are by that time anyhow...plus the planets. My guess is that the Earth is something like a planet-city, much like Trantor from the Asimov novels or Coruscant from SW...
Mercury, Mars, and the Moon wouldn't be far behind...nor the Jovian moons, perhaps even the Saturnian ones, and Pluto even.
When does it say the subspace drive was invented? sometime like 212-something...cant really remember. by that point, my guess is that the solar system has been pretty well worked...the Earth is at a level 4 (services and tech) economy, the other planets leaning more towards service industries, still with heavy industry (shipbuilding), then theyd move out to Delta Serpentis and the other systems...
By the time of the VT War, my guess is that Sol is like a capital system. If youve had 2-300 years to expand out into the galaxy, and youve got 15 systems colonized, then the original system has been pretty much left as administrative. Delta Serpentis would be close to there, and the other systems would be raw resource and industrial systems. Remember, with subspace, a cargo of food or metals from, say, Ikeya or Ribos, going on large civilian freighters would be able to get to Delta S. or Vega in a day or so.
The freighters im guessing would be large, slow, and close to defenseless, but with huge cargo capacity for efficiency. With subspace, they dont have to move too quick

If you cut off the capital system from the rest, i dont know what would happen...maybe like cutting off Western Europe from the rest of the world? i have no idea...
Im not saying they would be COMPLETELY useless, just that their production capacity and resource influx would be drastically cut down....