Alright, while a million other ideas spin in my head, here's one I'll share for free.
As it's just off-the-shelf parts, I figure it would be wrong to profit from it if it was a good idea anyways.
How do you pick up paintballs or reballs? Most seem to use rakes or scrapers to get them all together and then shp-vacs or shovels to pick them up.
How about an automatic way?
You'll already have compressed air at the field, so look into purchasing an "air operated conveyor". (Here's one manufacturer
) Essentially, once provided with a flow of air, you have an open-ended central vacuum cleaner.
Build a basin to sweep all the balls into below the intake, or use a flexible hose like for a central vac.
For reballs, direct them into an appropriate container.
For paintballs, a trash can. Or, for a niftier idea, direct them into a funnel.
Top of the funnel, a hose/nozzle. Bottom of the funnel, a sink garbage disposal. When the air operates, have the water and disposal run. Everything flushed down the drain.
Good Idea? Or bad?