Voters might want to read the other writeups first.
This depends on how the Borg thought system works. You propose a system that would be, in a computer metaphor, like the Everything database merging with the Microsoft Encarta database, and both having access to each other's information. From what I've seen of the Borg, I would think it would be more like Microsoft forcibly adding all Everything content to Encarta, closing the site, and taking Everything's servers to work for Microsoft.
The borg communication system is basically static hardware. The question is: How does The Borg know what thought is Correct and what thought is Incorrect. It's possible it's in the hardware, but that's unlikely. Equally, it's possible they have a 'truth committee' that scans everything and estimates the chance it is correct, but this is also unlikely. I would expect from what I've seen that everyone gets every thought, and takes an average opinion.
The problem with this is, unless when a thought is assimilated it is a self-contained, self-proving theory, all the people who have no idea balance it out. If when the Borg assimilate someone, if they have a fully proven theory, it will be accepted and used. Unfortunately, things like fashion can't be 'right' or 'wrong'.
So, the borg use an 'average' style. Unfortunately, styles do not rely on being average. They are often unusual and radical. Assuming style can be defined on a '-1 to +1' scale. An awful eighties style might be +1, because they were fairly radical. A late nineties style tries to get a long way from that, to -1. The average of +1 and -1? Zero. So, the entire Borg use a standard, identical and dull fashion system. What colour is dull and standard? Grey-black. And there you are: Your Borg fashion.
Another point for consideration is: What are Borg values? At what point does the Borg stop augmenting themselves because they look stupid? I mean, I could get real utility from an extra pair of mechanical arms. Great in a fight. Loads of uses. Why don't the borg have extra arms? And why do the Borg value utility over style? So many questions, so few answers.
I will try to add some answers in due course.