Radek,
We have been testing many different configurations in our labs involving MetroCluster within FlexPod, and the configuration you describe is essentially the version we have settled on to validate and release over the next few months.
We'll leverage MetroCluster across the dual sites for redundancy and failover, as well as 2 pairs of FIs for the server components, one pair at each site. The only major change from what you describe is that we are validating the Nexus 7K for the networking components so we can use OTV for the seamless migration of VMs and to support multiple failover scenarios. The Nexus 5K will be 100% supported and discussed in the CVD, but our main validation will focus on the N7K because of these additional features.
Please let me know if you have any other questions.
Dave