A couple of things regarding Champions.

[Thalatta]

First, champions is quite a misnomer. One would be hard pressed to find elite troops being called like that in any serious source. They are usually called, well, "elite". There's of course the issue that ranks are "Basic", "Advanced" and "Elite", the first two again terms that one will basically never find to describe how experienced units are. I think better would be "Recruit", "Seasoned" and "Veteran", all terms I've come across multiple times in sources.

Second, what about ships and engines being able to be "champions"? One could make use of elite triremes for Athens for example, instead of making up things that weren't characteristic for them. I guess the main point of champions is to indicate that organic units do not work, but I think there's also a "good unit" implication being made that could be useful for a few inorganic units (they could also have some particular restriction or characteristic, like auto repair? Repair only at Dock/Arsenal? No repair? Whatever is balanced).