With the old space grid, capital ship weapon ranges of 1 made a lot of sense. But since we're looking at a truncated melee for space battles, "same grid weapon fire" might be more advisable, which is a good observation. This is something we may consider changing for the final rules set. Glad we're mocking it out now.
In a GCWII mock, we tried out the "no movement after getting destroyed" concept and it gave a distinct advantage to ships that had movement of 2 over movement of 1, because they could fire from one grid away, destroy their target, and then run 2 grid spaces... thus preventing the destroyed ship from being able to return fire.
However, since all movement has been normalized to 1, "no movement after getting destroyed" might be best.
I think that's fair?