This book isn't about "what does the average player need", the idea from the start has always been "95% of the rules for 95% of the players when playing 'Mechs". Construction rules are not necessary to play a game, for example, but fire and smoke are probably necessary even if most people don't play them frequently because they're common enough to be included. This book similarly isn't limited by Succession Wars/Clan Invasion/Jihad eras along the timeline, so common equipment up to and including the Dark Ages should also be included, and also things like CASE II, Angel ECM, Superchargers, Thunderbolt Missiles, Mech Mortars, etc. I'd personally like things like Hardened Armor, Reflective, Reactive, Ballistic-Reinforced, and Ferro-Lamellor included, too.