Then we have to think about redundancy. The simple solution is to have an secondary NFS server and use DRBD. For the shortcomings of that read http://githubengineering.com/introducing-dgit/
The next step is introducing more granular redundancy, failover, and rebalancing. For this you have to be good in distributed computing. This is not something we are now so we rather outsource it to the experts that make CephFS.
The problem of CephFS is that each file need to be tracked. If we would do it ourselves we could do it on the repository level. But we rather reuse a project that many people have already made better than go through the pain of making all the mistakes ourselves. It could be that using CephFS will not solve our latency problems and we have to do application sharing anyway.