There it is, the fundamental design flaw with Halo 4. Reach didn't do anything noteworthy that warranted it being the basis for the next evolutionary step in the franchise. Armor Abilities as a whole did more to frustrate players and stifle the gameplay rather than innovate and push the multiplayer to new standards. Loadouts completely undermine the basic tenet of Halo multiplayer: everyone starts out equal and battles for the upgrades on the field. Reach failed to make even one solid map that I would like to see remade in this or future games, so the decision to move forward from that relative trainwreck of a game really showcases how diametrically opposed I am to Halo 4 basic design philosophy.
Exactly, Reach is not a game from which to build your new house on. To me, Halo is the sort of series which has perhaps earned the right to be considered in the same vein as your Mario's or your Zelda's... Or at least until Halo 3, it had the right to be considered in that kind of company with the amount of game on game industry leading innovations the series had brought with it (the first was a gameplay revolution with its two weapon limit and recharging shields. Halo 2 basically invented the modern xbox live lobby and interface and Halo 3 pioneered social gameplay sharing with its theatre and forge modes).
Mario and Zelda are among the best series' in gaming history and are essentially always their own inspired vision. This is what Halo had basically earnt the right to be: a sovereign title, unmoved by the transcience of industry trends, confident in the purity of its own experience.
Now this doesn't mean that the series cannot change and innovate from within but certain principles of Halo's gameplay have to be constitutionally protected and everyone starting equal, so everyone knows what to expect of their opponent, is absolutely paramount. When Mario jumps on top of a Goomba in any Mario game over the last 30 years, the Goomba dies. He doesn't suddenly armour lock in the latest installment.
I remember Frankie equating the uproar over the Halo 4 Game Informer reveal details to people disliking the introduction of dual weilding in Halo 2; at best that's misguided and you can't compare instant respawns, see through walls, camo with sprint on spawn and not being able to predict or control where the next power weapon is coming from to any change in the gameplay from CE to 2 or 2 to 3.
Using Reach as the base is a bit like the Mario team using Luigi's Mansion as the core for their next 3D mainline Mario title. Yeah the Luigi game is good in its own right but don't let it guide its big brother.