You know, I don't think we ever pinned down a definition. . .
I'm not being snide here. Just wanted to get that across. Forums just don't convey a lot.
"We". Well, I certainly know the definition. I've stood in rooms with a lot of higher ranked aikido people from across multiple schools and they certainly knew the definition. Not only that, but I heard a very common theme from people who had 20 to 40 years in the martial arts (not just aikido) after experiencing aiki -- they said, I can't do anything to you (you being the person with aiki) and I have absolutely no idea what you are doing. These people had experience fighting, sparring, judo, taiji, aikido, karate, taekwondo, etc and had seen and done a lot.
So when you say, "we", it really should be "I". Again, not being snide or anything. Just that I've talked to and seen too many experienced martial artists who have come to the same conclusion that I have after experiencing aiki first hand.
Now, I think Kevin is probably right in that some wrestlers, fighters, etc are probably using internal structure to a certain extent. And as you noted, some of the fighters are excellent. I certainly wouldn't want to get in the ring with them.
But aiki ... not really.