This seems to have worked. I had all 12 spawned and in addition 3 duplicates after I restarted M2TW, in a random order (different than yours). When starting the Dutch campaign, the priests are now selected from the entire range of 12. This was not happenning until I exited and restarted M2TW. So I guess the new portraits will not be available to current campaigns. For some reason the higher-numbered portraits are not save-game compatible.
At least there seems to be some kind of logic now. Thanks for your help.