SOINC decided to respond to this question personally. I don't know if you've seen it already, and I'm too lazy to check back 3 pages. But here's a definite answer. Looks like teamwork will have to do!
SOINC posted their reply more that 5 years ago. As far as I know, no one has ever been willing to pilot the idea because, while it is interesting, it is also logistically impossible.
Nationals already has a tough time accomodating the 60 teams from each division already.
For example, if Ohio had an All-Star program and sent an all star team with the first place winners in each event, it would have involved:
Solon, 9 events, 18 kids, Chardon, 3 events, 6 kids, Copley-Fairlawn, 2 events, 4 kids, Orville, 1 event, 2 kids, Mentor Memorial, 1 event, 2 kids, Revere, 1 event, 2 kids
Lee Burneson, 1 event, 2 kids, Amhurst, 1 event, 2 kids, Watts, 2 events, 4 kids, West Liberty, 1 event, 2 kids, and Northmont, 1 event, 2 kids
That is a total of 11 schools with up to 46 kids. It's really impossible to coordinate that many people.
Also, Solon is just a big school with a very dedicated program. They have multiple teams that study hard and push each other to do well. They are not unbeatable.