I can see wanting the node name for debugging purposes in the gtid (for the originator) and bqual (for the branch node). We'd have to make sure that we truncate names which are too long though as the limit for node names is currenty 255 characters (though we could reduce it further, as the maximum length of a host name label is 63 (recommended maximum length is 24)).
But what I'm not clear on is, why exactly do we need the other node names in the XID? I think that come out of off-forum discussions and without that information I can't really offer up any ideas. It seems like we should be able to take advantage of the unique topography of this scheme to provide some of the information.