What systems would you put into place to prevent abuse?
What about bad cops who would misappropriate the intel?
What would prevent them from tracking non-terrorist/drug related individuals?
How do you prevent citizens from being followed and tracked without a warrant?
And if misuse or abuse does happen, how is that transparently shared with the victim?
This is a weak place to argue that slippery slope doesn't apply, since the government has already had a lot of incidents in the recent past where they said they weren't doing certain surveillance - and then it was leaked that they actually were...
If you could say 100% that these balloons will only ever capture data based on legal warrants - we might have something to discuss. However, I can't think of a system that would guarantee that.