Thucydides wrote:No one has mentioned Hot Air engines or Stirling engines yet. Since early steam engines had a nasty tendency to suffer boiler explosions, Hot Air engines (of which the Stirling is the most evolved) were developed as substitutes.
These sorts of engines, while heavy and low powered like their steam counterparts of the time, provided much of the same benefits as steam engines without the danger. Indeed, had things gone a bit differently in history, these sorts of engines may have displaced steam engines in many applications, since they dispensed with the weight of the boiler and water, and the Stirling engine is the most efficient type of engine possible (working at close to the "ideal" Carnot cycle for heat engines).
OF course, like all engines, they also benefit from being built to close tolerances, which seems to be beyond the state of the art for the CoGA controlled territories.
An added benefit of stirlings is that you can build them with seals only on the cold side which is great as things like greased felt and leather compounds become possible.
However, there is a lot of subleties involved in designing a good stirling and the church not having the ressources of an helpful PICA wont be able to do it, I think