You can resolve DUPLICATE when there is a Brainstorm proposal open, and only in that case. Besides, Bugzilla ask you for a bug number to resolve that way, so you would neet to hack bugzilla. Not nice.

But I agree with the "rudeness" of the INVALID resolution and I have spent a couple of lines of explanation in the few occasions that I have resolved a Brainstorm case that way.

I wouldn't mind a BRAINSTORM resolution.