True, starting first thing in the morning would be the way to go if you decide to go to Himeji.
I can see the point of visiting the castle - it's really worth a visit in its own right. If the OP decides that's on his must see list (and I can understand that it would be), then I agree.

To call Hiroshima bland and suggest that Himeji is less bland is not a logistical point, though ... I don't know why people invent spurious reasons to support their points of view on FT.