I think a release gate that is spring loaded would work.
Made from plastic and attached at bottom of drone, maybe super glued?
When the tension on the line is greater than the spring, it opens the gate and drops the line/bait.
That way if you get a jag in spool it will just let go. When you want to drop the bait, put drone in sport mode and lower it fast then up fast and gate opens.
I can see a bit of trial and error in getting the spring rate right but you could do this on an oval.
Just a thought, and i can picture the device in my head. Could probably make money from it🤔