One assigns a prior to a class of hypotheses, and the cardinality of that set does not change the total probability you assign to the entire hypothesis class.
If one instead assigns a constant non-zero prior to each individual hypothesis of an infinite class, a grievous error has been committed and inconsistent and paradoxical beliefs can be the only result.
Agreed.
However, when you write:
> the evidence makes the uncomputable partial Oracle the most likely hypothesis, since the space of uncomputable partial oracles is much much larger
you seem to argue that a hypothesis is more likely because it represents a larger (indeed infinite) space of sub-hypotheses. Reasoning from the cardinality of a set of hypotheses to a degree of belief in the set would in general seem to be unsound.