Assuming construction had progressed as planned it would be possible to have the Impero completed in late 1942, possibly as late as early 1943. She does not differ much from the Roma. I've removed the director gallery between funnels 1 and 2 to add better arcs of fire for the AA guns. Impero also has a few more 37mm twin mounts to increase the AA firepower. Seeing as she's completed so late compared to the rest of the class, she is fitted with two radar mounts, as was the Littorio, probably because she was in for repairs as these ships seem to have a natural attraction (cough "fetish" cough) to torpedoes. I've also moved the directors that would have been in the director gallery that has been removed. Littorio class could never have enough directors. Otherwise, don't know what else should/can be changed that would make sense.
Impero as hypothetically completed in 1942:
Italian battleship Impero hypothetical appearence in 1943: