Reducing the ISO is surely what you need to do rather than increasing it.
Adding the filter would increase the amount of time taken for the camera to reach what it considers to be the correct exposure and should be helpful in this instance.
If by "exposure" you mean adjusting the "ev" values then I think that is not what you seek. This skews the exposure from what the camera considers correct and would result in either under or over exposure.
The above said long exposures generally require steady platforms, I am not sure if a flying drone would be steady enough. I have taken such shots with normal camera (normally tripod mounted) and will see if I can find them and see if any demonstrate camera shake