I really, really wish I had your levels of optimism. Truth is I just don't see it happening given how they've handled multi-forme Pokemon thus far:
Having Castform dynamically change forme in your box might have been too complex of an endeavor for something very few people would notice. A Ditto-esque mechanic where it changes upon being sent out to battle would be cool but it would pretty much lose any STAB it would have had unless you routinely changed its attacks before sending it out. A workaround to this could be to give it one set of moves for each forme similar to how Ditto takes the attacks of whatever it transforms into.
The announcement specifically said you can catch Deoxys in its Normal forme. To be able to change it on the fly would make this statement a little redundant. "Transforming" EX raids could just mean that it's the first EX boss change in ever while being a nod to its gimmick in the main series, not necessarily indicative of them implementing it.
The Giratina thing was just one of many recent bunglings with the Gen 4 rollout. The game master (I think) currently has the 9% nerf applied to anything that goes over 4k CP, released or otherwise. The promo art for the Halloween event and Gen 4 release video showed Altered forme, why would they do this if Origin was meant to appear first?
Also the game master lists each forme as separate entities, meaning they are not one and the same.
Also also whenever the Giratina with the bungled CP gets powered up its CP drops to what Altered forme should have.
Prepare for disappointment; multi-forme Pokemon will likely continue to be handled this way unless fan outrage grows big enough to hurt them financially. Rotom formes will probably be research related like the Spinda patterns, Shaymin may or may not be special research related netting players one of each forme, the djinn trio will probably see separate releases for each forme, I have no idea if they'll even acknowledge Arceus, much less how they would. I'd love to be proven wrong about these but given what we've seen and how much they like to pad content I expect this to be par for the course.
EDIT: Missed your bit about the Sinnoh Stone the first time around.
This likely is meant to be a universal item for the plethora of cross-gen evolutions that require specific items. Honestly this is fine in my book. I'd rather one item for all of them than have them individually add Shiny Stone, Dusk Stone, Razor Claw, Protector, Electricizer, Magmarizer, Razor Fang, Dubious DIsc, Dawn Stone, Reaper Cloth, and whatever their solution to location/moveset based evolutions would entail. Maybe the Shiny and Dusk stones will be added separately since future Gens use them but the rest can be lumped into one item without harm.