In the end I feel we would have reverted to a round ball because of cost and ease of feed.
Given even the price for a FS round being equal to the price of current paint, due to the ease of feeding and the far smaller package to hold it you would see .68 rounds fitting in because of that.
FS, at best, could be loaded into Q-loaders or similar. You can hold twice the number in a standard pod.
It would kind of be the .50 cal argument. Except .68 cal would work in the range that people are accurate and get into firefight with on a regular basis. After 100ft, most people don't hit things. Shoot, in firefights 'trained officers' often miss people at near point blank range.
While I agree on the tournament side hitting reset and having only FS rounds hit the market first, there would be larger, more technical fields. But give your front players far more rounds possible and a fast feeding setup that is lighter and they are able to carry more in a smaller package (just a couple pods, smaller TS1 styler loader) and they would go in to eat them up. I remember when we went from a simple game style to run and gun. In the end, run and gun wins. That dictated the game style, the fast aggressive paint hungry play works and well! Give players the faster feeding, faster loading, more rounds per shot reset, I wouldn't be surprised if .50 cal would be a better choice. Cheaper, more per loader/pod, well suited for aggressive play.
Edit: Also add smaller tanks, less kick, higher ROF (less bolt travel) less pain, smaller hoppers, shorter bolt travel (for simpler internals) and the list goes on.
You know, I would say reset to .50 cal.