Michael Piller’s Fade In is an interesting behind the scenes view of the development of Insurrection. He basically started with a couple of ideas and scenes in mind (Picard vs. the Federation, aging and the fountain of youth) and tried to construct a script around them. I don’t think there was ever a good idea to begin with, but it’s interesting to see how the script developed and had to be changed as he played his ideas off of Berman and ran up against budget issues and input from Stewart.Insurrection-Make the Baku the bad guys, because they already were. (And it goes without saying, don't make the TNG crew support them just because Picard wanted to get his geriatric dick wet from some centuries old hippie bitch.) That doesn't even invalidate the central conflict of the movie. The Federation wants the fountain of youth, because they're in the middle of the Dominion war, and could use the medical help... and the Baku are assholes who perched there and they don't want to share. Hell, have the Baku ally with the Dominion. (Because the immortal Founders don't even need a fountain of youth to begin with.)
I hated the idea of the Borg Queen as soon as I heard about it. It got even worse when she turned out to be some kind of horny spinster. The chilling thing about the Borg was exactly what Q offered up: you can't outfight them, you can't outrun them, you can't negotiate with them. They're one vast, faceless, gestalt being made of zombie cyborgs, driven and calculating, but also emotionless and kind of mindless. Very instinctual, like a swarm of army ants.
Then in one fell swoop they were given a face, that of a moustache-twirling Ayesha ripoff subject to flattery and bamboozlement, and made into her slaves. I don't know about anyone else, but for me it killed the concept and the threat of the Borg.
I can’t remember where, but I thought I read (maybe in Piller’s book) that the script writers introduced the Borg Queen because they felt they needed a villain that the cast could interact with and trade lines with.