You still neglect the issue.
If you have the power to wield, hypothetically whats stoping you from using any keyblade?
IE: Riku using Oblivion.
Why doesn't Sora use the Way to the Dawn? Sora doesn't have that ability but had Riku's Replika been created after he acquired it the he would have that ability. Having the ability to wield doesn't automatically give complete access to all Keyblades. If it did then Mickey traveling to the Dark Realm would have never happened seeing as he already had the Star Seeker, he could have just transformed it into the Inverse Kingdom Key, but seeing as that's not the case he had to find it to obtain that ability to wield it. Riku using the Oblivion is the same as Kairi using the Gayblade, it isn't the same as wielding because the ability to wield is different from temperarily borrowing someone else's weapon.