I think it entirely depends on how you plan to inject the new values into a running program. If you are doing iterations, then it might make sense to do an IOref that contains the entire space of values that may change and then atomically update the whole space when a config update happens. Or maybe you can put each update in a queue inside of an IORef and then do an atomic modify, or I see there is a package providing lockfree queues in hackage. Again, I think it more depends on how you are going about running your program, and where it makes sense to inject new values.
Charlie