As a nod to the ridiculous inclusion of ETs species in the senate for TPM why not have some ET ships at the landing site and ET at the Separatist's board room meeting?
When they all deliver their little declarations of allegiance ET's head could pop up and scream (from the scene when Gertie runs into the room and they both scream at each other).
Similarly the EEV Pod in Watto's yard could result in a monolith from 2001 being one of the Separatists too.