Allow customization of Armor, Engines, and Balloon. Part of your ship customization would be selecting one of each, allowing you to tweak passive stats a bit to fit your strategy, at cost of course.
Armor possibilities:
Lightweight Armor, gives 15% speed and vertical speed boost, 20% less armor.
Regular Armor, gives normal stats.
Heavy Armor, small 15% increase in durability with significant 30% decrease in mobility.
Ablative Armor, starts with 20% more armor, loses 10% max armor per rebuild for a final value of 20% penalty after 4 rebuilds.
Hardened Armor, + 10% armor, -20% hull.
Balloon possibilities:
Helium Balloon, takes half damage from fire stacks, -30% lift.
Armored Balloon, +30% balloon hp, -20% lift, -10% linear speed.
Aerodynamic Balloon, -30% balloon hp, +15% linear speed.
Synthetic Balloon, +20% lift, -20% balloon hp.
Regular Balloon, stats as current.
Engine possibilities:
High Performance Engines, +20% linear speed, +20% turning acceleration, -30% engine HP
Filtered Engines, -20% linear speed, takes no damage from tar or sand.
Steam Engines, half damage from fire stacks, -30% vertical speed, -10% linear speed, + 10% engine hp.
Vectored Engines, +25% turn acceleration, +25% turn speed, -10% linear speed, -20% engine hp.
Regular Engines, stats as current.
More variety = more strategies = more fun!