@DennisS and others.  I have dozens of palm tree stalks in possession.  My tentative plan is to use the chain mechanism of a bosch micro chain saw, having an overall effective length of about 3 inches.  

Your described task of removing a single random frond from a palm tree is likely beyond the ability of the proposed machine.  The general art is to remove the lowest effected fronds and move up.  I think this can be achieved by a drone.

Fronds falling on the drone could be prevented by a temporary frond retaining ring, but this would add another step and take too much time for commercial acceptance.  I think a more acceptable solution is to offset the cutter from the main drone body laterally and use light weight plastic mirror assemblies to redirect the video image to the target.  I agree that the mass and ballistics of the sequentially falling fronds would otherwise make a dismal statistic for drone survival.  

@ABitRusty and others.  I do not know how to link videos here, so I will provide title and provider info on following YouTube video “agrimate arecanut harvester-sprayer (kannada)” provided by shramajeevi tv.  I want one of these bad.  It looks like the cord disengages a clutch.  I like that the operator can provide torque on the cord to spin the device around the trunk.  

Everything is compact enough that it could be hauled around on a bicycle trailer.

@ABitRusty and others.  I do not think that the drone could survive a work week without wrecking.  At between $600 and $1k per drone, that would not be sustainable.