Kyurem-B should have never been dropped to OU to begin with. That monster single-handedly dismantles stall teams, has no real counters, gets a lot of free switch-ins against extremely common 'mons like Politoed and it can kill 2-3 mons per match (at worst) with zero effort.
It might be "slow", it might be weak to SR and common attacking types and it might lack an extensive movepool, but it gets the job done so disgustingly easy you'd have to be a moron if you're using Kyu-B and fail to get free kills.
The Mamoswine/Magnezone/Kyurem-B core is gaining popularity on PS and those who have used or faced it will tell you that it absolutely dominates early- game. You're almost always guaranteed to set SR, trap and kill a steel-type and kill something else with Kyu-B. It's so easy to use it's not even funny.
"Could I use Arceus in OU if I give it no EVs?" "Can I use Politoad in NU if I don't give it any good moves, and just use it for drizzle?" "Can I use Breloom in UU if I use Effect Spore?" Etc.
If you open the door to allowing something only if it meets some specifications, soon you have to do it with everything.
The thing about that is, as so many people emphasize when players are annoyed when their favorite non-legend is made Uber "UBERS IS A BANLIST! IT IS NOT SUPPOSED TO BE A BALANCED TIER."
People are not arguing for letting high-tier pokemon into lower tiers with certain stipulations, they are arguing for the removal of a Pokemon from the banlist with a single stipulation, a stipulation which is not at all complex.
Removing a single move or ability from a single Pokemon would change only ubers who were not intentionally made uber. Pressure Lugia is just as Uber as Multiscale, Kyurem-W would still be Uber without Overheat or Draco Meteor, since Fire Blast would still be an option.
Arguments about using ubers without EVs or at low levels are ARE needlessly complex, because A: even without EVs, 670+ BST Pokemon will still be at an advantage. And B, testing for low levels is nebulous and time consuming compared to the removal of a single move or ability, in which case it can easily theorymon it's viability after the change.