Steampunk COG/Vamp/Ghost occultists


Nothing in the manual says a COG, Vampire, or Ghost cannot be a psychic. In fact the Occultist class description says COGs rarely see the point but sometimes do. So how long can any of them maintain a Trance? Additionaly the lack of Con to add to Concentration checks makes the Vampire and Ghost which are listed as "the occult personified" at a serious disadvantage without having the Con modifier to add to it, that just seems contrary to itself to me.
I was trying to figure this one out too. In the beginning section of the Monster Manual for D&d 3rd (and I'm assuming in the OGL), under the description of the traits for undead creatures, it says since they don't have a Con score they use their Charisma modifier for concentration checks.
In my campaign I have given this trait to Cogs as well. Even though they are constructs, and cannot be resurrected, they still have some form of potential to tap the forces of magic. But you could come up with some unusual characters. A cog priest that can turn undead. Cog shamans that commune with nature spirits. The amazing Coggini who can talk to the ghosts of your ancestors fire only 5 gold pieces. You get the idea.
This small rule adaption taps into one of the basic ideas of the Cyberpunk genre as well. Mainly: Are sentient machine truly "alive"? Do they have what we call a soul?