There won't be a singular optimal build, there will be a changing meta of which stats to focus on for the specific pokemon. Now a standard attacker just needs 31 IV SPD which is boring and just a waste of time. What if you could invest for example in more ATK to the decrement of SPD. This would allow for far more meaningfull and varied team compositions.
This system would of course only follow after extensive rebalancing. It's a shame that smogon needs to clean up the mess gamefreak makes, if you want to use a substential amount of viable mons.
I don't care what the game designers once thought how the game should be played. The reality is, if you are serious about PvP you need flawless Pokemon. They should have come to the same conclusion.
It's also baffeling how the story of game and anime contradict it self with the actual game mechanics.
Physical sweepers would max out attack at the detriment of special attack. It doesn't really matter if that's EVs or some system that's exactly the same but more complicated and tedious. Your system would boil down to max EVs in attack, no matter the complexity. There will always be an optimal build in Pokemon. Some Pokemon might have a handful of optimal builds, but they'd still exist and no amount of complex raising special attack to lower attack training will stop that. It will just make a system that's already kind of tedious (but getting better) into something more tedious.
The anime is getting better about not contradicting the show. I actually watched an episode awhile back that explained abilities, and I never thought they'd bother with those in the anime, since it's a very "gamey" thing. Also Pokemon in the anime only ever know four moves, which I think is actually pretty cool and faithful to the games.
Smogon also doesn't "clean up the mess Gamefreak left." They don't do anything but organize the insane amount of data and complexity of the game into a nice and consistent format. They can't change that data, and some of Smogon's rules are rooted in rules Gamefreak themselves invented (like Sleep Clause). Smogon doesn't do any re-balancing and many of Smogon's bans aren't allowed in Gamefreak tournaments anyway (like many legendaries).