Eh, agree to disagree. I prefer the 3rd SW to be the sandbox that it has been. We already know that it was a long, low-intensity war. It ranges from 2866 to 3025. The Successor states couldn't even keep up a sustained, organized campaign without severe financial hardship. Even by the time of the 4th war, Operation Rat almost bankrupted the FedSuns. The whole nature of the 3rd war was small raiding actions, a seesawing of borders, a select number of short & grander actions, and a continuing degradation of technology.
So, do the house handbooks go into details as to why certain things like going bankrupt to conduct a campaign? Of the ones I read, they haven't. A book that can flesh out why things happened the way they did would be very welcome. Since it is the era of constant raids, they could even go into why raiding was as successful for the house units, let alone merc units, as it was, or wasn't, however they decide to run with it.
There are a lot of gaps in the nuts and bolts of the BT framework, applying setting to game and/or vice-versa. Even a small book can add lots of interesting extra tidbits that might make you rethink how things are done in the BTU and what the BattleTech Aesthetic is supposed to be.
Secondly, I'm not real keen on hunting down old FASA stuff, even in PDF form, and trying to piece things all together. There are plenty of new people that probably have the same disposition. Having a non-Fasa, non-Fanpro CGL book that puts all the little things together would be awesome for new players and players who came in late.
I missed out on all the 80s and 90s stuff. And, having found some of that stuff, I find a lot of the information in the various scenario books to be a little light on information. I was hoping for a little bit more.