[Q]

Originally posted by Mephisto:
The AI will only build one system wide facility per system. Maybe more if you call them by different abilities but not when using the same ability.

This is not completely true. The AI will check only if there is already a facility present in the system with the system wide ability but ignore facilities under construction. Therefore several identical system wide facilities may be constructed at the same time and eventually present in the same system. I see this all the time.
A possible solution would be a special colony type that is only chosen once per system and then put all the system facilities on this colony.