Mocking the average fic-writer's inability to come up with original ideas is as noble a pursuit as any, however...
Everyone's argument against trunks with rooms seems to be the lack of ventilation.
Aren't they forgetting that Moody spent the better part of a school year at the bottom of the very same trunk that made the 'multi-room trunk' a cliché?
Sure, they're in every story now, but they're also canon; something that can't be said for other clichés, like super-wands with eight cores and a fist-sized diamond at the tips, goblin credit cards, and the Imperius Potion Bellatrix took on the night of her forced wedding.
shrug
Yeah, I know I'm preaching to the choir about those last few things. Hehe. People knocking on trunks with bedroom-sized compartments just leave me scratching my head sometimes. :)