Given where it is and the likelihood of this recurring in the lifetime of the platform the options are rather limited.
1. Is there enough strength in the mirror & coating to avoid damage?
2. If there is an impact & damage occurs, how much can you sustain before the capabilities are degraded?
3. How much adjustment do you have to correct mirror alignment if an impact duffs up more than specs on the coating?
One assumes that this was all calculated into the design but being rather pessimistic and the huge cost over runs on the project, one wonders.......
It will be really sad and somewhat ironic if JWST is outlived by Hubble. There is a planned life of 10 years with an expected life of 20, I just hope that continued exposure to events like this does not screw that up. Bluntly, if it is anything to do with hardware that cannot be corrected by software or post image processing then it is stuffed.