Might be an interesting idea for a UAV like this to include a mount point at the top where you could attach a helium balloon that could carry some percentage of

Might be an interesting idea for a UAV like this to include a mount point at the top where you could attach a helium balloon that could carry some percentage of the weight less that 100%. That reduction in weight would translate into longer run-time. Of course it also would reduce maneuverability.