Are you sure? It seems to me the paperwork involved is a whole lot easier than the emotions involved. You aren't really saving much head/heart ache by living together first as a trial.
It takes a lot less time, effort, and emotions to simply discuss the things first. Plus you can meet a lot more people in that time, vs living with each one as a trial.
You might say "so is living together" but I know people who started living together just because they are already having sex so might as well combine finances on the rent and groceries and they don't really view it as a huge step.
Not heart ache, but you'd be saving a lot of headaches by living together before marriage. Finances these days... retirement accounts, who paid what into the house... It can be a huge mess.
Yes, probably by at least one trip to a lawyer and at least one trip to court, regardless of relative difficulty of dealing with the paperwork and the emotions.