Handbook for the Houses took many years to make, that's why they were in 3067. Closest thing we have for handbook for the Republic was the Field Manual: 3085. Frankly, it would been nice to have more. Era Report: Dark Age is another book that has some elements needed, but frankly isn't enough.
a lot of that is also conditional. At the time, the game market was coming off a massive downturn (late 1990s through early 2000's saw more than one crash), and while the House Books (the 3067 ones) were extensive-they were also begun prior to the FASA collapse, and a lot of them dated to before the mid 1990s gaming industry implosion.
flash to MWDA and a lot of it is 'recovery era'. MWDA started during the period that FanPro was still acting as license for both Europe and the U.S. , Catalyst was a suggestion, and just getting their feet under them, means finances were tight and licensing was an issue. (the "No Published Fiction" era, and the Dark Age Novels)
this means a lot of what might've made it into a sourcebook series or series of novels? wasn't going to either because of IP control issues (Who gets to run novels? who gets to run short stories? how much of your sourcebook can be fiction?) and raw finances. (Total Warfare was
expensive, the whole collection of hardbacks were expensive both to produce, and to distribute.)
There's a lot of externalities involved in why the Republic never got t heir own book, and that's not counting the feedback from marketing and fan reactions and how those can be interpreted by the guys who have to pay the bills.
Plus, they were hips deep in the backstory of the Republic already with Dawn of the Jihad, including trying to resolve the individual blurbs Wizkids put out with special unit cards to fit and work with the prior story materials while allowing something to progress after.
and Catalyst was not a huge operation at the time-neither was Fanpro. My contributions to FM:Mercs were paid with what amounts to a regular (not cashier's) cheque, because of all the infrastructure they were still dealing with setting up at the time.
It's kinda useful to acknowledge that this is a business, and it's a volatile business, sometimes the thing you think is ideal can't be done, because the resources just aren't there compared to where they ARE going-which is usually toward the safer bet until there's enough slack to actually take risks. When the FM books rolled out to the stores? they were set up for an era that was pretty sure to post profit of some kind, or at least break even. in the early 2000's there was no guarantee that Wizkids' success would carry over to a sub-license property in the right way.
basically a LOT of the fans treated MWDA as "Klikkytek' and ragged on (and raged about) it unfairly.
so there was a lot going into that. It's unfortunate that they capped off the Republic era the way they did, I suspect a prolonged
war arc would've been better storytelling than what was delivered, but that's smoke out the casing now.