Try to think of it as an exercise on a blank board not with hind sight and a preconceived idea of a an end result.
Actually, that's how I tackled each and every alternative to evaluate its likely probability.
1. Why Luz? I don't believe it is Luz per se that is important. The characteristic of the OC was it had a very high percentage of families with children aged under 4. It also has a non-secure security system. Unlike many or most resorts it uses mechanical keys, not computer key cards that can be tracked. As it so happens, it was early season for Europe, ruling out many destinations (as David Payne testified).
2. From memory, M has eyes of different colours. I see no reason to build in an eye colour requirement, on the basis that this would have required an awkward bit of checking. Therefore the recipe is fair skinned, possibly blonde, female, passes for a 3 year old.
3. There is no need to build 5A into a plan, if it is being done as a blank board exercise. If Ella O'Brien had disappeared, we would be talking about a girl of similar description (hair colour aside) disappearing from 5B. 5B had the same unsecure security system, as did all the apartments on the ground floor of blocks 4, 5 and 6.
4. The generic client was someone who could pass off a 3 year, white skinned girl as his/her own, if the target spec is correct. This rules out large swathes of the world re skin colour, but leaves large swathes as potential destinations. So much so that I don't see how OG could systematically eliminate such countries. It requires a sighting, followed by investigation of the same. That is not systematic elimination by country.
5. The route I've got does not require the 'gang' to hang around hoping. The team assembles once informed a suitable target is in situ. In this scenario, only sightings occurring after the T9 were in place relate directly to Madeleine. Other children may have been monitored earlier, but such sightings, if there are any, relate to Madeleine's disappearance only indirectly (possibly same team).
If the requirement WAS for a fair skinned, 3 year old girl, Madeleine could still be alive and well.