Let's go back to basics for a moment.
SR says that c is c. A different speed in different directions would mean SR is wrong. GR builds on SR, and cosmology builds on GR. So it's not clear that this question even makes sense.
Actually, I think it doesn't make sense as asked, although it may be possible to pose a well-defined similar question. Or maybe not? If you don't have spacetime, what does it mean for spacetime to be curved and the universe closed? If you have spacetime without SR, how exactly does this work?
Next, let's examine why you can't measure the one-way speed of light. You need a distance, a time, and a synchronization convention.
Sagredus: We don't need a synchronization convention because the light comes back to you.
Salvatus: Provided you are at the same point. How do you know that?
Sagredus: Um, absolute space?
Salvatus: There is no such thing. How do you know you receive the light at the same place you emitted it? After all, there are two parts to a synchronization convention - space and time.
Sagredus: If you move from A to B, you feel the acceleration as you start and stop.
Salvatus: Not if you are moving at constant velocity.
Sagredus: But you can tell if you are moving!
Salvatus: How?
Sagredus: Relative to the fixed stars! Or, if you like, in a frame where the totality of the rest of the universe has no net momentum with respect to you.
Salvatus: That is picking a synchronization convention. One can do this even in expanding FRW universe, if one could imagine such a crazy thing. The time is measured in comoving frames relative to the big bang. A person at one place shines a light at another person, and tells that person how many seconds it has been since the big bang in his comoving frame. The second person knows the time the pulse was sent, how to synchronize their clocks, the distance between himself and the source, and off he goes to calculate. He will of course get c, because that's a consequence of his synchronization convention.
So, I believe that if it were possible to replace the question asked by a similar question that is well-defined, the answer would be "you are picking a synchronization convention. The most obvious one, so obvious that you don't even know you are picking it, gives c as the result of the proposed experiment."