I agree with Ceric. Hyrule Castle in SSB64 and Peach's Castle in SSBM both WERE the castle. This one is a part of the castle, but doesn't encompass to the same extent.
It seems that most of the Brawl stages are just different platform arrangements with pretty backgrounds. I was also a fan of the larger stages of SSB64 because they lent to more strategic combat in lieu of "you're cramped together in a small space, now fight" type of levels.
I'm sure there will be others, but I vastly prefer the stages were you're fighting on a piece of Nintendo history, not in front of it.
For this stage, wouldn't it be insanely awesome if you saw a siege tower pull up to the castle in the background, then a load of soldiers pile out, then another one pulls up to the actual platforms and a load of soldiers pile out and the players need to KO them?