Drake, the idea was trading out armor for a lighter weight alloy and increasing the amount of manuver thrusters.
OOC // basically a ship that can manuver through asteroid fields a little easier by trading bulk for engine power. Just remember, to a merchant if a ship can not make it through an area with some degree of success then that route is unusable. The solution would be to craft a vessel to compensate for the short comings of existing ships in relation to those trade runs. I think the best way to represent this is look at the ship design system employed by Traveller. This is a PnP game that came out in 1976 and is still going very strong. Using a system like that as an example allows ship design to be balanced and consistant. In that system you could trade out armor thickness to get more room for additional points into manuvering without losing cargo space.
