Unfortunately, with a B+Tree index, you cannot jump in powers of 2 (well, you can but only within one page). To find a record with a given offset you'd need to traverse the whole linked list of the leaf-level pages, and that's what MERGE JOIN does by default.

However, this solution would be nice if you had a sorted recordset which allows efficient positional seek (for instance, a materialized result of the previous operation which required sorting).