A detailed analysis of all available info seeking further info as and when required.
I cannot be sure of the time as I don't find any of the T9 testimony reliable in this regard. I'm not convinced GM physically checked the children at circa 9 pm and I'm not convinced the others were checking as regularly as they claim and/or they were checking round the front via locked doors.
In my opinion it is not possible for you to be in possession of enough information to make judgements such as you express in your posts for the simple reason that, unlike the present investigators of the Judicial Police and Scotland Yard, you do not have all the information to enable you to pontificate.
They have the information and unlike the investigators of 2007 there is evidence available that they have actually used it.
The information in the files available on the internet reflect a moment in time frozen in aspic. There were many more individuals in Luz on the 3rd May 2007 than those you have chosen to 'investigate' and much more information from the time and the subsequent years thereafter.
Neither Mr and Mrs Moyes or Mrs Fenn were checked out at the time despite being in the building from which Madeleine disappeared, or in the days following ... hardly standard police procedure one would imagine.
I think you have fallen into the elephant pit of sceptics which fails to take account that there were more people in Luz than Madeleine's parents and their friends and although they kept quiet about it until a fortnight after the event ... the Smith family.