... but now ahead of MAD, FCO, etc. Maybe it's because I'm a natural pessimist, but I must say my line of thought is very much along the lines of NickB here. It is also the case that airport layouts vary basically every time, and that also means that solutions and how good they can be will vary too, especially as you need to caliber the area for "safe flights but non-Schengen" to a space more or less commensurate to their actual passengers and aircrafts' volume. You also need to allow transit to themselves (usually easy) but also both from non-Schengen + security rescreening and to Schengen (without security rescreening) whilst also maintaining a route from non-Schengen to Schengen with security rescreening from non-safe origins.

Some airports like AMS have a central area which means that you can put a single passport control point, for the whole transit flow, and a single security rescreening point - again for the whole transit flow - and those two needn't be in the same place, and you can even allocate proportions of non-Schengen gates to safe and unsafe quite granularly without much trouble thanks to the existing piers system. Great. At CDG, however, there is simply no equivalent so whilst there may well be a solution, I must admit that unfortunately I can't think of it as "obvious" just off the top of my mind.

I'd also suggest that even amongst the examples that you mention, it is far from the case that all are perfect systems. For instance, I admittedly haven't used FRA since covid so maybe they have found the Graal now, but before, it was the case that even for LH-LH connections, ability to transit from a safe non-Schengen flight without rescreening security was - as of early 2020 - not universal and depended on which gates you arrived at and went to which was a pain in the back! (in other words, I specifically had to re-clear security despite arriving from the US more than once at FRA including in February 2020). Again, maybe things have improved since, but even if that is the case, it only serves to illustrate that FRA certainly did not get it right from the start and if improvements occurred, it has literally been years after the system of non-rescreening from safe arrivals was first introduced and involved a lot more than simple common sense adaptation or will. By contrast, MUC was far more straightforward, but again, it is a very different layout from CDG. The very simplicity of its layout making the sequencing of passport and security transit points easy and efficient. CDG is a hugely messy design in comparison and ADP a generally poor operator so i don't really expect them to come up with miracles any time soon i'll admit!.