I've been thinking about upgrades and thought briefly about collisions between balls and higher power launching and think that's a dumb idea. You have a very nice amount of force and gravity here. Gravity does affect it, but it's not super powered. If we start changing ball speed, the gravity will have no meaning and I don't think it's worth the loss of the balance you have between force and gravity.
Little robots to go pick up the blue gems for you, or a magnet or extra range upgrade on gem pick ups are missing and would be appreciated. Even an upgrade to get half or 10% of the gems on the ground at the end would be close enough. This does need something to pick up the exp.