@Mouse and others.  Arborist (light weight but full sized) chain saws are typically used.  The scale of the photo may be misleading but the chain saw I am considering is about as long as a pinky finger (ring finger if you play a 3/4 sized cello).  

@ABitRusty and others.  Currently coming back from a month in upper Florida.  

When my wife was on the beach, I noticed the town’s highway crew trimming palm trees along the street right of way.  So I took my bicycle and cell phone (stop watch) and did a sort of time/motion study on the crew of three.  The trees were rather small (from about 12 to 18 feet tall).  Two people acted as traffic control/frond gatherers.  The last member was in a bucket truck with a gasoline powered chain saw.  Another crew of three picked up the frond piles with a truck mounted hydraulic clam shell loader.  Six staff and about $200 k of equipment.  The process seemed very capital intensive and inefficient.  

The staff told me that the biggest problem was wasp nests in the trees.  Swinging around the chainsaw is tiring and they try to switch out the chainsaw operator a few times a day.  

So I started to think about the process using first principles.  

I know nothing about helicopter drones, but the design that most interests me is made by intel (see photo).  Those cost $20k.  The consumer product that seems the most suited in terms of operator interface is the dji mavic.  I think that I could parallel the wires going to the four propeller motors so that I could package 8 motors (like the intel model).  Speed is not a big issue here and I might obtain more payload lift by using a 3 lobe propeller.  But the biggest gain in payload lift would be gained by tethering the drone and supply power from the ground.

I already figured out that a vacuum cleaner cord return mechanism has power contact rings that I could use.

The cam shear mechanism used by Jamie (above) has a lot of difficulties.  So far on my list is an oscillating saw blade, counter rotating dual circular saw, hot wire, and Bosch micro chain saw.  The frond stem has a hard outer coating and a soft inner pith, which should not be too hard to cut through.  

If a drone is used, something would be required to retain the vertically pointed fronds while they were being cut so that they would not fall on the drone.  So hard the craft, so little the time, so very much to learn.

@ABitRusty and others.  Regarding the fire hazard of the hot wire.  Perhaps spraying the fronds with water from an inexpensive pressure washer as a preventative measure?  I think the moisture content of the living plant should be adequate for the small thermal input I an taking. 

I would like to be able to do 3 per hour.