It's not possible to reduce all lawsuits to compact formulae. Part of the legal profession is in interpreting old laws in the modern context, for instance, which would take something close to a general AI. More broadly, reasoning about legal edge-cases needs a sophisticated understanding of the law and of the world. Also, jurors can't be replaced by software, as they must be 'peers' by definition.

I imagine it would be much easier to build a system to roughly estimate the odds of a lawsuit being successful, inputting salient features of the case and running the numbers, without deep reasoning about the particulars. I don't know if work is already being done on this but I wouldn't be surprised. A lot of money must ride on knowing which corporate law battles can be won.