Thank you both. I know from glancing through the catalog and my own resources there are a number of Mercenary ____ books, and while most seem like fluff or additional resources for information, they are not rule supplements.
Yes. The Mercenaries Supplemental 1 and 2 books provide profiles for mercenary units that others have created. So if you need a quick look at various forces for inspiration, there you go. Field Manual: Mercenaries is largely the same thing (I think ~75%), but also contains rules for creating units, negotiating contracts, etc. as well.
The unit creation rules in FM:Mercs have been replaced by the rules in Campaign Operations.Mercenaries Supplemental 3 focused more on the "dark side" of the BT mercenary trade. Those mercenaries who were pirates or some other kind of ******. They also updated some of the mercenary unit briefs. I can't remember off the top of my head, but I think there were rules for generating your own force of ****** pirates in there too.
Again, rules for creating your own pirate ****** were replaced by the ones in Campaign Operations.