As for golems i think about workshop.
Because i thought about:
Siege workshop - 20 hp (yes, lower), 8 turns to build, 0/3 armor.
(all these are mechanical units (can be repaired by workers) and immune to fire and ALL spells excluding damaging, curse and slow)
Steam tank - amphibious unit with moderate hp (25-35), moderate damage (10, can be increased by "Advanced gunpowder") and armor (3/3), carry capacity of 2, moves freely in both land and water but at cost of lower speed in compare with regular ships and wagons and bonuses to ships (speed 3, can be increased by 1), cost 6 turns, can be built by workers for 15 turn cost
Submarine - invisible water unit with low hp (15 or less), extremly low damage (2-4), no armor (can't gain), speed 4-5, melee range, ability: "Fire rocket" - fires rocket at water unit dealing 50 (debatable) piercing damage, range 3 tiles, cooldown 1 turn (once per 2 turns), cost 4 turns when near water, can be built in TC.
Siege engine - unit with low hp (20), high armor (6/6), low damage (6, can be increased by "Advanced gunpowder"), medium range (6 tiles), normal speed (3) and trebushet bonuses to buildings, has researchable ability "
Barrage": gives +20 damage and +2 actions/turn but lowers range by 3 tiles for 1 turn, cooldown 6 turns, cost 4 turns. Can be built by workers for double cost (8 turns).
Helicopter - Low hp (10-12), no armor (can't gain), extremly low damage (1, can be increased by "Advanced gunpowder" to 7), range 3, power range 1 (can be increased to 3), speed 5, sight 7, huge bonuses to air units (500-700%), cost 3 turns.
Armored Golem - good hp (40), moderate damage (10), great armor and p.armor (7/7), speed 4 , carry capacity 1 (Infantry and workers only, can't carry giants), cost 5 turns
Battle Golem - good hp (40), good damage (15), moderate armor and p.armor (3/3), speed 4 (5 after research), bonuses to infantry, cost 5 turns
Assault Golem - good hp (40), great damage (20), low armor and p.armor (1/1), power range 1, speed 3, bonuses to giants and buildings, cost 5 turns
Mithril Golem - Great hp (80-120), huge damage (40+), great armor and p. armor (9/9), power range 1, speed 3, bonuses to buildings (halved standart ones), cost 8 turns
All golems are count as Giants, amphibious (speed 1) and fight in melee range.
Battle tank - unit with great hp (70), good damage (20, can be increased by "Advanced gunpowder"), good range (5-7), normal armor (2/2), speed 2, can be carried by steam tank, carry capacity 2 (infantry and workers only, can't carry giants), has researchable "
Fire grenade" ability (renamed fireball, cooldown 2 turns, range 4 tiles, needs to be researched first), cost 9 turns.