Assuming you're talking about the late Succession Wars, the problem is that FASA already covered it in detail, so any book covering would only be catering to new players and the 3025 or bust group, and for the former new art would be required.
I’m not in the camp advocating such a thing, I simply was empathizing to the viewpoint. Personally I’m happy with the chosen direction
But consider for a second the idea that the late succession wars are “tapped out” due to extensive previous coverage. The last late succession wars sourcebook produced by FASA was 20 Year Update in 1989 with a few callbacks in scenario packs like MAC and Battle Pack: 4th Sw. Brush Wars and War of 3039 are fifteen years old already. It speaks poorly to the future demographics of the game if a new player is someone who missed our on books OOP for nearly thirty years. I started in ‘96 just after 4th ed was released and the only way I learned about much previous to the clan invasion was because my friend’s uncle had some of the late 80s stuff. A second question: what about the even more exhaustively covered by FASA early clan invasion is any more appealing to vets? If the argument is been there, done that the only universally acceptable era is 3150.
Further, a classics-based box wouldn’t be any less new-player centric than the first box. Old hands are mainly in it for the minis. I’m guessing most people here would fail a pop quiz on the contents. I think a more important question is asking what new players want from an expansion box. Are they happy with no or few new rules or equipment with the expansion being in new units and background? What expectations have their experience from playing other games with expansions created? I ask because I have no idea.
Again, I think the clan box works better with the current product line, but I think we need to reconsider philosophically about how we think about the product line in general.