I haven't balanced a blade in yrs. Also have had no spindle issues in several mowers.Interesting idea but I'll pass.
As you mentioned Mark, obviously the blades don't get balanced.
I scrape and clean out the deck just before putting sharp blades on. So I have to get down there anyway.
Looks like you still have to get down and rotate the blade edge to the front (middle blade) or to the side (side blades) so this tool can reach it.
How long will that camera last with metal grindings flying all over the place?