Unless your model actually consists of a large number of Python objects (and not a handful of PyObjects referencing something like a np array), there isn't real

Unless your model actually consists of a large number of Python objects (and not a handful of PyObjects referencing something like a np array), there isn't really anything blocking you from doing so. You can have a master process map the blob of static data into a block of shared memory that's mapped by the secondary processes; ctypeslib lets you access it as a numpy array again.