Why did they do this. was the Ent just a sneak peak for beta players? It felt more special when it was the oddesey, so i hope they change it back.
I think it's possible that it was just a special preview of the Odyssey for the test shard players, Although I think the Galaxy Dreadnaught looks pretty scary in the Mirror costume too.
If it is intended to actually be replaced by the Dreadnaught, they may have figured it would make better sense story-wise if they introduced it to us on the normal side first, during the upcoming Cardassian Featured Episode Series, instead of seeing it first from the Mirror Universe and then looking like our UFP copied the design from the Terran Empire.