Based on Paredit keybindings, I don't think 'sibling', 'union' and 'splice' would be enough for convenient editing; you'd at least need a set of keys to move nodes (with their subtrees) around.
I'm thinking it would if you also had good selection keybindings.
click on node -> select-family -> command-x (family gets highlighted similar to Excel) -> select target node -> use sibling or append-child (implicitely moves the family in the clipboard)
The only other special move you need is a switch-position between siblings. for the insert actions it would be best to have next-sibling and previous-sibling (alt-arrow left/right like iWorks tables?) and last/first child.
