how would you approach it if you need to install as follow:

Prod site: FCI over 2 nodes

DR: FCI over 2 (or single) nodes

AlwaysOn between the two FCIs

So all 3 (or 4) nodes must be part of same WSFC. what if the were both already running prior to your AlwaysOn plans, how do you 'combine' the two separate WSFCs then ?

then with shared storage, each FCI set has shared storage only between then, not between sites. how would you set this up in Cluster Manger / how do you validate the cluster and tell it to validate the storage only between 2 Prod nodes, and also validate the storage for the 2x DR nodes only, if all 4 nodes are in the same cluster now?