The only average exit velocities we can record from live ABs is in our national indoor hitting league.
We do record live ABs when they stand out in games. Actually TrackMan does that. And when we use TrackMan all the data gets entered, so I guess we could find a TM exit velocity average, but it would only include those that hit when TM was being used, so not really a true average.
To me "average" exit velocity against pitching, not off a tee, is a very important number. Not only shows peak velocity, but average shows consistency of squaring up pitches. Obviously the biggest problem with average exit velocity is the quality of pitching. But in cases like the indoor hitting league where all the pitching machines are set at equal velocity... You could make an argument that the very best hitter would have the highest "average" exit velo, no matter what the other statistics said. Without knowing for sure, I would bet the top hitters in MLB would also have the top "average" exit velocity over the whole season.
Still that doesn't account for the most important things of all... Being able to hit high level pitching, breaking balls, etc. But that player that had the highest average exit velocity, would be someone scouts should want to see ASAP against good pitching.