Maybe one issue we haven't touched on is what does the gun show give us in return for our guns. Do they check everyone who comes in? Do they provide armed security for those who are inside. Those are generally my two conditions for the fair exchange. I used to work in a building where everyone was searched and armed guards patrolled. Therefore, since someone else was closely guarding me (Marines actually) I did not feel abused by not carrying.
I don't think the problem is so much inside the venue, but out in the parking lot. Lot of folks carrying valuable (unloaded) guns and big wads of cash. Seems like that is where you would be vulnerable. Some shows I've been to aren't in the best part of town and outside security is non-existent.
A clearing barrel at the entrance for loading/unloading a carry gun, which would then have to be kept stowed and unloaded on one's person with the ammunition separate seems like a reasonable compromise to me.