I wonder, does your ring consist only of the SCALANCE X 204-2 and the SCALANCE XR324? If so, this connection would be a redundant point to point connection with two optical connections (two fibers each) used.
If you think about using only two fibers... which would be one connection you have no redundancy.

Connecting the numbers of network devices you mention should be no issue.

The only thing I think about is... do you maybe use PCS7? If so I think I remember the recommendation to split the plant- and the terminal-bus. I guess to keep the traffic away from the plant bus and to improve the performance.
So if you may live with the possible restrictions, go ahead.

Best regards

I think you may work the way I sketched with this post. As media modules you will have to use MM991-2 modules with 100Mbit/s on ST plugs.

Best regards