Many thanks for the answer. It really helps.
I have another question about the WSIs. It is about stations that already have an identifier (064XX for Belgium). For these stations, an automatic WSI number is associated depending on the affiliation program. If a new station with the same affiliation is created, its WSI will be generated from a different scheme. It means that for an affiliation program there will be two schemes. And the old stations (064XX) could also have a WSI in the new scheme. It is unclear for me if you can/have to use this new WSI or not. In our internal discussion for the new scheme development, users prefer to have one scheme even if it implies extra changes. In our communication with WMO for those "old" stations are we supposed to use the adapted WSI (0-20000-0-064XX) or could we use a new one derived from our WSI scheme?
In the WIGOS guide it is mentioned that "old" stations "May or may not continue to use the pre-existing identifier as the value for the local identifier" but it appears in contradiction with the guidance to avoid several identifiers for one station. So can we decide to stop using the adapted WSI (0-20000-0-064XX) and switch to our WSI scheme for international data exchange for all stations managed by us? And what is if any the best option from WMO point of view?