It probably wouldn't be profitable, but it would nice to have little A4 sized "handbooks" that cover one class, or a small group ("The Fighter PHB" or "The Martial PHB"). Just includes only the items a single class would access. Maybe with extra subclasses, gear, backgrounds or races closely associated with the class.
And I'd gobble up if they came out with a modern version of the old 2E Player packs - semi-rigid burlap/cloth or hard case, PHB (and space for the likes of a supplemental book - like Tasha's or Xanathar's forecoming replacement, character sheets, minis or acrylic stand-ups, set of dice, pencil, condition tokens and a hit point counter.
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