Contemplating the idea of a two wheel launcher, but how should I get the balls into a tube or mechanism that stores the four allowed balls until they can be launched?
I’ve heard of a conveyor (using tank tread), side rollers, maybe even a top roller. For your case though the conveyor might be the best option in regards to storing 4 balls and putting them in your outtake system when you would like.
Otherwise keep searching the forums if you run out of ideas.
top roller then conveyor belt will most likely be the best choice, however top roller might work as when u keep adding more to the ramp, the last will come in contact with the launcher which will the then give u some more room on your bot
The tricky part is going to be dealing with the stack of balls, intake for balls on the ground is relatively straight forward and front rollers etc will work. Coming up with a way to reliably collect all 4 balls at once from the stacks will be the trick.
Then you also need a point in your design where you can insert the driver control balls.
This one scaled up on a robot would work. 
^^^ Yes ^^^^
Something else that will effect that is how easy it is to knock the stacks down. If this is a very small force, might it just be better to knock the stack down, then pick up the balls?
For sack attack my team used a spatula type of intake. It didn’t work too well for that game but it would have no problem picking up the pyramids in this game. If you could find a way to alternate between some kind of other intake and the spatula plate thing then you could pick up individual balls and the stacks easily.
The spatula simply slides underneath the stack and a motor rotates it to dump the whole stack into a hopper at once.
This will be interesting. It seems to me that just the robots driving around could shake the field enough to tumble those little stacks (especially on an elevated field).
I feel sorry for the field setup crews who will have to re-position those balls 352 times before every match…and then again when a student breathes on the field and they all come tumbling down.