Wim,
It would be possible to add Festo fittings, the reason I don't fit them to the CAT range is mainly due to two things.
Firstly they are more suited to pressure applications rather than suction, and secondly being a complex fitting there is a bigger chance something will fail resulting in an air leak. A barb is like a key, its simple and very good at its job if correctly used/designed. A pipe pushed over a barb and security wired will in my opinion be far more reliable than any push fit type fitting.
Wim, appreciate your support and happy safe flying.
marcs