On the contrary, you seem to be working very hard to defend a theory which is not supported by what we know. No-one has to 'make do' with lack of evidence, it's the one suggesting a theory who needs to find something to underpin it, not those being asked to believe it.
Your first post on the subject mentioned weak security (keys) Advance information (booking system) and control (allocating accommodation). You suggested one person in particular had knowledge of and access to all three.
Many more than one person could have had the knowledge and access, so the 'one person' assertion falls down.
It isn't possible to know if the MW system made a difference because we haven't seen booking information from other operators, so advance information could apply to all bookings.
Without a motive for allocating clients to a certain block, the 'control' serves what purpose?
OK, lets try it step by step.
Cruciform keys. According to Heri, he nipped into the Luz high street key cutter and asked how much it was to get a copy made, the answer was €6.50. According to me, the cost of a machine to cut cruciform keys in 2007 was ... €300.
Do you consider that cruciform keys, which are as common as Yale keys in the UK, and which can be duplicated for €6.50, within Luz, are secure?