[Alneyan]

The current patch is 1.1, but a 1.2 patch is in the plannings (some of the bugs you mentioned will be corrected; others slipped past my attention though, such as the size of the Caravan, not to mention the Ghost problem)

Mobility is the ship equivalent of Afterburners in the stock game, and not a proper engine (Movement is). So it is, and should indeed, be limited to one per vehicle.

The Resistance component works as an "armour" against Runes of Petrification (Engine Damage) and the various fear weapons (Weapon Damage). Resistance has a very high structure, which makes it much more likely to be hit when these special weapons make an appearance. But since it is also an engine, every Resistance component you put will lower your maximum speed; so you cannot use this component to become completely immune to Engine/Weapon damage, or to gain "cheap" hitpoints.