it is a very nice feature, that Xpression can fire GPI (out) to trigger other devices.
Especially the Smart GPI´s (TCP/IP) based are quite helpful.
Unlikely these GPI´s can only be fired by writing a script.
For some of our customers this is quite difficult to handle, as these guys are no programmers.
On the other hand, prime systems are providing GPI by datasheet, but no scripting - means that outgoing GPI´s cannot be used. ;-(
My recommendation: Could you link outgoing GPI´s to the events used in scenedirector. GPI´s could be used then also for the prime system and are much easier to handle for most of the users.