--- What if, instead of requiring an engine to be at least 1,250 Tons and at most 50% Power to be considered Commercial, it was changed to a drop down that let you choose between Military and Commercial with Commerical doubling the tonnage and halving the power? Crew would scale to as normal, half power = half crew and whatnot. Commercial engines would still get the bonus to fuel efficiency same as they do now.
Two problems with this:
1. This makes the definition of a commercial engine murky, confusing, exploitative, and pointless. For example, if I understand this correctly I could make a 200% boost engine and click the "commercial" checkbox to have a 100% boost engine at 2x the size... I've designed a standard military engine that reads as commercial on sensors?? You could avoid such silliness by changing the suggestion to say that any engine with 50% boost is commercial, but in that case all we are doing is removing the size restriction which has already been put in place for a game design reason.
2. This requires making an "exception" in the game rules, when the design thrust of C# has been to reduce or eliminate such exceptions.
It is also worth noting - commercial engines do not get a special bonus to fuel efficiency in C#, whatsoever. The improvement in fuel efficiency for a low EP boost modifier is the same regardless of the engine classification.
I'm also unsure what problem this suggestion is trying to solve? We will always have an arbitrary commercial vs. military designation in Aurora, because the mechanics of it are too essential to the gameplay and frankly necessary to keep the level of logistics micromanagement down to reasonable levels. Given that, having a simple and clear distinction between what does and doesn't count as commercial makes much more sense than having a complicated mechanic just for...what reason?
--- If Commercial Engines get no fuel efficiency bonus above and beyond the typical, then that's fine, but the point is that a Commercial Engine can be used Commercial-y. It is valid for no maintenance designs. The Military Engine with 200% doesn't have this ability, while the commercial engine does, but trades away the power and instead gives that mass over to the ability to be No Maintenance when on a Commercial Design. Using Commercial Engines on a Military Ship thus have no utility anymore, since the No Maintenance is wasted.
--- This streamlines the how and why, since we can assume the how is that whatever is being used to make the Military one go 200% is halved or being used to the effect of making a smaller one at 100%, while using that space saved to add the Magic Doesn't Break Smoke that makes Commercial Engines do their thing. Likewise, the arbitrary engine size and power limit is no longer an arbitrary limit, but a flexible one with a simple toggle that asks the player: "Is this for a Warship or Not?" Another problem it solves is not being able to make tiny Commercial Ships... or even FAC sized ones, to be honest. Currently every Commercial ship MUST exceed 1,250 Tons... before Crew Quarters, Fuel and the lot.
--- What will this be used for? Currently Fighter-sized cryo is bugged since Fighters still can't land on planets to offload colonists... so that's of no use. However, the addition of Small Craft Refueling System means a No Maintenace FAC tanker sees a good benefit from this change. Likewise with Deep Space Populations and the renamed Orbital Habitats... a centralized Colonist supply could be established with Commercial FACs / Fighter scale colonist shuttles refilling the "stock" Tiny FAC sized or smaller scouts receive a good benefit from this, since they would need no maintenance and no additional deployment for their missions, being able to relocate under their own power and hang around forever.
--- Finally, this does not create an exception to the rules at all. Commercial Engines are ALREADY an exception made more exceptional by the arbitrary limits. Jump Drives ALREADY use a toggle to this end, but regular engines don't. Such a toggle streamlines, simplifies and brings regular engines into line with the Jump Engines that they mechanically interact with. This eliminates a special mechanic rather than makes it more complex. A toggle is straightforward, highly visible and not confusing to a new player who wouldn't realize it's 50% or lower AND has to be AT LEAST 1,250 Tons.
--- Hell, while we're at it, why not do the same for sensors? Give it a dropdown to tag it as Commercial, same size, but half the strength... but putting it on a ship doesn't make it military?