The shield’s native ability is to protect Bella’s mind from direct magical intrusion. Anything she adds to it has to follow pretty directly from that, although she can modify it in any or all of several directions from there (canon Bella focused entirely on making her shield extend to other people, which never occurred to luminous Bella). She managed to make the shield protect her mind from direct physical destruction, but indirect physical destruction would be something else entirely. Especially since her mind’s survival is never going to be necessarily dependent on her avoiding any single injury that isn’t being set entirely on fire (and she’s got limits as to how much she can stand being set on fire, too).
She’d have to fight against her shield to join the hive mind, not to mention that the hive mind wouldn’t readily have her.
So, “If they can hurt me, they’ll rip me apart and set me on fire until I die” won’t work to make herself nigh-invulnerable?
Or, for that matter, “I need allies if I am going to survive the Volturi, therefore I need to join the still-free pack’s hivemind”?
The shield’s native ability is to protect Bella’s mind from direct magical intrusion. Anything she adds to it has to follow pretty directly from that, although she can modify it in any or all of several directions from there (canon Bella focused entirely on making her shield extend to other people, which never occurred to luminous Bella). She managed to make the shield protect her mind from direct physical destruction, but indirect physical destruction would be something else entirely. Especially since her mind’s survival is never going to be necessarily dependent on her avoiding any single injury that isn’t being set entirely on fire (and she’s got limits as to how much she can stand being set on fire, too).
She’d have to fight against her shield to join the hive mind, not to mention that the hive mind wouldn’t readily have her.