Well to answer the subspace question, lets discuss another question. If command captured Shivan Fighters, what would they find? First of all we grabbed their shielding technology, wiht some modifications. Now look at this:
In FS1 when we grabbed their Sheilding technology, sence they were able to inter-system jump Then; Why did they not figure out their engins, and grab that technology. They didnt and would have, they had peacetime afterwords, and a whole war or to to figure it out and impliment it in GTVA fighters and ships. So that conculds either that command blew up the technology on accidnet (likely) trying to figure it out, or the shivan fighters did not have the technology then. Unless:
If a captial ship inter-system jumped, maby theirs a.. a pocket around the main Cap, cause it has reactors to power the I-S jump; So the fighters if close enough could travel along too, in the bubble, and not use anything But their regular engin power.
How dose that sound?