I get it now. I had a very broad definition of support, wheras you had a finely honed one.
To use the mage as an example, the "necromancer" fits my term of support, because it offers a new playstyle for that class. However, it doesn't fit yours, because existing mages cannot honestly swap out spells for the new school. To fit your definition, support would include new powers for existing schools.
Specifically, the necromancy build options (i.e. the fixed bonuses they get as they level, like the pyromancer's ability to ignore fire resistance) are not something that can be swapped in.
The powers, however, are support for all wizards. They may not directly reference and support older builds, but they could be useful for other wizards. The necromancy school therefore comes with built in support for wizards by providing more options that are available to all.
My argument was in terms of "the old class is not being supported" because (a) it doesn't provide new options, like implement masteries, (b) the powers built for the new school won't be (as) useful for older wizards, and (c) they won't provide direct support for implement masteries.
If the definition of support is needing to have direct support for the old options, it would require either tons of new powers with rider effects, or as you pointed out do exist, powers with numerous different rider effects depending on which build is used; this is especially true if the definition of support is that something that is tied to a build (i.e. it has a school's keyword built it) is only considered support for that build. If the definition of support is entirely new builds, it still doesn't help existing characters.
Why could WotC not do something similar to make the powers work for both old and new builds.
Zomg Lightning Spell, Level 33, If you're a invoker wizard, get this bonus, if you're a staffizard, get this other bonus. Completely vague example, but I think it gets the point out there.
They could do it, but they shouldn't need to. Not only do most of the classes being supported have lots of support already (clerics, wizards, warlocks), but a power doesn't have to be tied directly to a class feature (which only a percentage of characters of that type benefit from) in order to be useful. An, in the case of the schools (and most of the masteries) there are benefits that don't require an explicit mention for it to support the build. A good save ends effect is good for orb of imposition. Orb of deception, and all the schools, are based on keywords to look out for, etc.
I just don't think that players need the power to say on it "Btw, this is good for this particular build" ... as most of the time it should be pretty clear. And, the reason it wouldn't be clear is that there are way too many options already (in which case adding more options isn't a good solution).
Also, referencing many older books is likely not in the plan. That is something better suited for dragon magazine content (since the people getting the magazines have access to all the old content via the compendium and character builder). They don't want a new book to tell someone picking it up "Oh, to make use of this you'll need to have PHB1, and Arcane Power, and the Heroes Books, and PHB2 and PHB3 and the settings books since we reference those races, etc. Essentials was, in part, an effort to lower the barrier for entry (and, by making Essentials evergreen, always available ... so that anywhere selling Heroes of Shadow should have the Essential books, but may not have copies of PHB1 available. If the support relies on you having the original build to make use of it, they wouldn't include that kind of support since they don't want to encourage people to buy the introductory product that is now very outdated, both in terms of rules that have been errata'd, but also class designs that have been abandoned. Why encourage more people to complain about lack of support for conlocks, and strength based clerics, etc?
