A throwback to something in a show's inner 'workings', yes. The thing is that a Shakespearean Haruhi gag within Seitenkan wouldn't work for the very simple reason that there's no logical reason for it to exist. If it did exist, half the school would be seeing it. Don't you think that Haruki would hear of something like that, especially if Itsuko was in it? Don't you think once he did, he would spend all of his time trying to figure out why something that was replicating the last few months of his life in gender-bent form exists, or had existed? The self-referential nature of the gag interacts really badly with the character's, or one specific character's inherent curious nature; if Haruki ignores it, then he can't be Haruki, and if Haruki follows it up we lose the story we've built entirely.
Also, it's not really funny at all.
And you're pitching this as though you were some kind of used car salesman, and then blaiming the customer for not buying their 'awesome deal'. Get a grip. <i>It's a bad joke, and I don't care.