When was the last time a new armored unit got demoted?

Literally never. Aside from Effie and Sheema going from 4-5* to 3-4*, there has literally never been a demoted armor unit.

Until there are several 180 and even a 185+, I don't see them making 175 chars 4*. Amelia should get a demotion, no point in her being exclusive anymore and zephiel should be included in summoning pool as 3-4, for red fairness. DC still needs to be 5*locked imo. All other non seasonal armors are still too good for being available so easily.

I feel like regular Hector should be demoted to a 5-4* rarity at this point. I feel as if he's outclassed now, hes not bad but Amelia and B!Ephiram are just better at this point. DC would be a lot more common, but you would need to premote him in order to get it as it will still be 5* locked. But if not Hector, Amelia is the best alternative. Just make her 5-4* but 5* lock Armor March.
I feel like that could work. But I totally don't expect them to do it.