And you still need a looooong barrel and a fast moving plutonium part (see the thin man design on wikipedia and then extrapolate from there) even creating near close enough pure plutonium since economically you won't have pure.

"Parsons’ first order of business was the plutonium gun. Because it needed a muzzle velocity of at least 3,000 feet per second it would have to be 17 feet long. It should weigh no more than a ton, a fifth of the usual weight of a gun that size, which meant it would have to be machined from strong high-alloy steel. It would not require rifling but needed three independently operated primers to make sure it fired. Parsons arranged for the Navy’s gun-design section to engineer it."

- Richard Rhodes - The Making of the Atomic Bomb

Can you rotate a plutonium "carousel" fast enough and then make all the pieces crash into a wall, onto each other...

Edit: Idk, something about flywheels, they can store a huge amount of energy and release it very quickly.

Probably not, we are talking really short timescales here. The nuclear explosion is over before you can even see the first crack in the housing of your bomb.