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.
In the vein of the Harry Potter and the Methods of Rationality discussion threads this is the place to discuss anything relating to Alicorn's Twilight fanfic Luminosity. The fanfic is also archived on Alicorn's own website <strike>(warning: white text on black background)</strike>.
Previous discussion is hidden so deeply within the first Methods of Rationality thread that it's difficult to find even if you already know it exists.
Similar to how Eliezer's fanfic popularizes material from his sequences Alicorn is using the insights from her Luminosity sequence.
Spoilers for the fanfic itself as well as the original novels need and should not be hidden, but spoiler protection still applies for any other works of fiction, except for Harry Potter and the Methods of Rationality chapters more than a week old so we can freely discuss similarities and differences.
EDIT: Post-ginormous-spoiler discussion should go to the second thread. (If you have any doubt on whether you have reached the spoiler in question you have not.)