The are plenty of deep state three letter agency traitors who could usefully fill Alcatraz.
One is unconvinced of the practicalities, but OTOH people who live within view of it would point at it and say something like, "That's where ****i lives", or "That's where *****k lives" which would be pretty cool.
At the end of the day let the guys who would have to rebuild it have some say. It would seem that another really really secure prison in... oh just random say Louisiana, way far down in the swamps, would be an equal deterrent...
Or way up north. So long as it gets built and populated with DeepState criminals like ****i and *****k et al.