Can you make a way to automatically remove empty bucket from generator like vanilla furnaces do?
I.e. if you put a hopper under furnace it will drop empty bucket into hopper if you using lava buckets to feed the furnace.
Or other option: generator will accept liquid fuel like combustion generator from Ender IO mod.

The generator is meant as a last resort incase you don't have any other mods installed capable of generating rf. However that is something that should be implemented so it will be in the next release.