ADS-B just doesn't seem like a sensible solution. The only traffic you'll have is VFR, and they don't even require ADS-B out if they don't fly in controlled air

ADS-B just doesn't seem like a sensible solution. The only traffic you'll have is VFR, and they don't even require ADS-B out if they don't fly in controlled airspace. It seems that having ADS-B out would just clutter up the system and not be terribly useful. I think the only viable solution would be to have sensors on the drones themselves -- visual and perhaps low-power radar. That way they should be able to avoid other drones and helicopters. It might be necessary to limit operations to VMC, although that shouldn't be much of an issue at below 500ft (you're only really going to be shut down during fog).