If a Stud breaks then yes it would need drilling out or removing However ......
AFAIK The top has 3 studs/bolts and the bottom has 2. Both the bottom "studs" are part of the old CAT so if they break you only need them repaired if you refit them, they are replaced with a nut and bolt when Berks go on.
2 of the top "studs" again are connected to the CAT so same applies. The third "stud" is part of the manifold end and is the one you really dont want a problem with, if it snaps then you would drill it out and replace with a nut and bolt.
I have done 4 sets of Berks and the next one I have to cut and weld will be the first! They are a good fit mate