If it tears bad it's technically possible to send up a shield that floats near the telescope. There were some plans for that way back during the design phase if I remember right. Still wouldn't be cheap or easy
It looks from the renders like the telescope has solar panels, antennas, etc on the sun/earth-side of the shield. Wouldn't sending a standalone shield screw that up as it would shade them?
Probably, although you could shape the shield not to.
It's still far more complex than just attaching the thing right to the telescope. And glancing starlight leaking in between the shield and the telescope could be a big problem.
I looked it up, the original proposal was actually to use a mobile shield to occlude far away stars for direct planet imaging. I think a similar approach could "fix" JWT but let's hope we never get there