Hi Binary,
I would echo the wise words of my old mate Heathrow Director. Multiple lineups ensure maximum runway utilisation, especially for a segregated mode operation like Heathrow. Pilots should know their position in the sequence, having been given a conditional multiple lineup clearance subject to only one aircraft ahead. (His number in the sequence is useful here). Use of intersections can help, subject to the intersection departure not taking too long to line up after a full length departure, and bearing in the mind the extra one minute separation if a medium or smaller follows a heavy from the full length.
Some qualifying points. Ensure that there can be no confusion about the departure order, by effective marshalling and precise identification of type and company of each aircraft in the sequence. Do not give multiple line ups to too many aircraft - no more than eight would be about right. Do not use in LVPs!! Do not issue line up clearances too early, i.e. before a pilot can see the holding point and the aircraft he is to follow. Ensure that the clearance is feasible, i.e. the subject aircraft can physically taxi into position without impediment.
That's about all I can think of at the moment. In summary, multiple lineups are necessary for expediting traffic. Any other ideas out there?