Since there are no facts that supports any of the 2 scenarios, I will say that the Bridcage strings would tear the bubble apart since a bunch of DF-users tried unsucessfully to stop the cage strings from moving.
Following "one piece logic" I am inclined to say that Kuma's paw-bubble isn't invincible (since it is made out of "air-like" ...
This lie has turned to truth - "Assisting in bringing down a bombman."
On little guarden when Zoro, Nami and Vivi was stuck in the candle he fought against Mr.5 and Miss Valentine (Mr.5 is a bombman, he said so him self on whisky peak) and won by freeing Zoro so he could beat Mr.5.
After the time skip Chopper is able to access all the transformations without the rumble ball. The Monster Chopper transformation he unlocks when he eats three can be done with one now, though he is still incapacitated after using it. Not only that. He can control himself while in Monster Chopper form.