The will of the Force has been Lucas canon since 1999. This idea of the Whills would be an exploration of that concept. In no way does it have to negate free will, because the will of the individual can be as strong as that of the Force, if that’s how the author chooses to see it. The Whills and their plans for the universe would be GL’s answer to what destiny is and he has, for years, claimed that the idea of destiny in Star Wars is that we all have one but that we also have the ability to choose whether or not to follow it. So essentially, someone going against their destiny is a battle of wills - the individual vs the Whills - and the short-term victory always belongs to the individual, it seems. I believe interesting dilemmas could’ve arisen from exploring this idea. Someone could, for instance, have thought “Since the Whills control everything, I might as well just look after myself and leave them to it”, thereby beginning their descent into darkness.