Several tiers of materials for constructs could be implemented. You could have layers of production so you would create the chasis in the forge from iron, steel or whatever and create the fine mechanisms elsewhere. Mechanisms of copper, heart of gold, crystal lenses etc. There's tons of potential for creating the many components needed to complete a final automaton with the payoff being the automaton is stronger.
Additionally you could have its abilities based on the materials of the components. A bronze mechanism would make it faster than a copper mechanism and a lens made from rarer gems would increase its skills in combat.
Hell I would love for there to be many tiers of golems. For example when starting out in a new area I would create a wooden golem and imbue it with life through a ritual and the only components needed would be wood, two gems for the eyes and successful prayer at the altar (20% success, components lost on failure). Same with stone golems but with slightly higher material costs. That way I could have quick and expendable defences up in the first year with proper preperation.
Edit: For metal golems, how about balancing their higher strength with vulnerable joints? So a strike to the arms or legs would have a chance to shatter the knee or elbow or sever it outright if the golem is not a top tier or war grade production.
Edit2: The best golems should be artifacts! So a smith claims a golem forge and needs components made from very specific materials. Also the only way to obtain mithril or better golems!
Edit3: Here's what I imagine a steel golem would require.
One heart of gold, created in the temple from a gold bar and one fuel.
Three advanced bronze mechanisms, created at the tier 2 mechanics workshop.
Two sapphire lenses, created in the jewellers workshop.
One Steel chasis, forged in the metalsmiths forge from 10 steel bars and the three mechanisms.
One copper dynamo, created at the tier 2 mechanics workshop.
One ectoplasmic remnant
One golem core, created from the heart of gold and the ectoplasmic remnant in the golem forge.
That's just my imagined scenario though