First of all I want to say great work on all of these. Mad props to you both technically and aesthetically.
However, my problem with the one-ship-one-insignia-each rule is that from a purely design POV, when you have a fleet in the thousands it gets harder and harder to come up with simple, distinctive and recognisable shapes before you start recycling and adding minute variations.
Back in TOS days I don't think this was an issue. I'm at work (shhhh!) so I can't look up hard canon on this but the impression we got was that intially there were only 12 "starships" at the beginning of TOS. Even if every other ship in every other class at the time had their own insignia, it'd be a good bet that the whole of starfleet wasn't much more than two or three hundred ships...and that's if we include all the ships listed in Franz Joseph's unofficial tech manual.
It's a solid point, though, that after a while there's only so much you can work with in making such simple symbols unique. One could theorize that the reason for the adoption of a standard starfleet insignia around the time of TMP was the fact that the fleet was ballooning in size and the fleet's graphic design interns had better things to do.