A couple of points about merging.
1. The rule says "If two Shadow vessels of the same type (variants are permitted) are in base contact at the end of the Movement Phase, they may merge". Can a third join in by moving into contact with one of the two already merged, or is it limited to exactly two?
2. The speed of the merged pair is half that of one ship. However, they merge at the end of the movement phase, but can break apart at the beginning of the movement phase. Which means that if I read this correctly, this rule can be abused. Ship 1 makes its move; ship 2 moves up to it and merges. Next turn, ship 1 breaks off and moves at full speed, then ship 2 moves at full speed, ends its move next to ship 1, and merges again. I'd suggest either allowing the merged pair to move at the full speed of one ship, or add a restriction that a ship which has broken from a merge can't take part in a merge the same turn.