I often option drag say a Process List node and go to rewire it and it wont accept the cables. I am guessing* that this is something to do with the nodes auto-converting to the node variant particular input and output data type.
When nodes are locked to some datatype there could be some visual indication on the node, a symbol or something/anything. When copied nodes should revert to a state as a newly instanced node from the node library. Unless they've been copied with other nodes and still wired to these other nodes.
Please change the FR title to better reflect this request and the underlying issues if this FR is in fact relevant.