I'm not in the legal world, so my experience is limited from a coding perspective. I don't think AI could ever truly come up with novel arguments, at least not yet, but their value for you may be to sharpen your arguments or pull on every thread that you may not even have thought about.

For example, theres a very popular coding skill set call Matt Pocock's Grill Me where it just asks you a relentless amount of questions about the feature you're trying to build. You may be able to tailor this somehow to act as the opposing counsel and have it poke holes in your argument. I suppose the closest analog would be a sparring partner.

Its helpful for me and my ADHD brain because I can go down all sorts of rabbit holes and it can easily keep track of all the ideas i have while grilling and it can send sub-agents out to investigate other claims to add more context to the grilling session.