With RevisionDelete in action, the only time that delete + partial undelete is needed is for complex history merges and fixing copy/paste moves.
It seems cumbersome that admins must repeatedly delete and part-undelete to selectively move revisions and repair cut/paste moves. If there was a "selective revision move" feature (RevisionMove?) that allowed administrators to select various revisions on a page and move them to another page somehow (in line with the needs of page merge and copypaste fixing), this would greatly simplify page merges and copypaste fixing. In fact there would be no obvious remaining need for selective revision deletion; it could all be done using RevisionDelete and RevisionMove, simplifying admin work considerably.
As a further thought, if RevisionMove were created, then partial delete/undelete could be withdrawn, and the link breakage bug 21279 would mostly cease to be an issue.