Mediators help sides to talk and develop opinions. They do not make judgments and can't do anything binding. It works best if both sides want to talk and have a vested interest in resolving a conflict. It's better than court in those circumstances, but that's a pretty narrow field to work in with a much bigger field outside.
Someone who sold you a house that falls apart or shoots your daughter has a vested interest in the status quo and walking away, not in talking about it.

And though having fewer, less complex laws makes for fewer criminals, most laws start off simple and get complicated to take care of the loopholes created by having simple laws. A noble sentiment, but hard to put into practice. Throwing out hundreds of years of legal precedence from the sober minds of the judiciary is tempting, but I defy anyone to improve on it as a whole. I think that will become more of a mute point as expert systems are getting much better at sorting through piles of legal documents. Free legal advice from expert systems may happen in my lifetime (maybe, or at least it would be possible), which would simplify legal matters.

Stable economies don't come from "Low taxes+ Strong property rights + consistent stable regulation" Strong economies, yes, but not stability. Did any of those three things stop or reduce the last banking crisis that pretty much took down the world's economy? No. Consistent stable STRONG regulation has a partial effect on economic cycles, but it still can't account for when when greed takes over everything else.. But who regulates? And who makes it strong, with only mediation?

Actually, I've worked a bit in the weights and measures industry. And devices that weigh and measure have to be certified and sealed against tampering so they can be trusted. Yes, that could be done with private firms, but the level of trust would be a lot less. And trust is needed for economies to work. Hundreds of other standards need enforcing. Do you trust pharmaceutical firms to tell you the truth about their products without verification? They have been caught fudging or ignoring their own tests many times before. What about food inspection?

I agree that some level of decentralizing is better, but I'm not sure why you think that will make everything better. It brings in a bit more accountability, which is why I like it, but it largely just changes the problems, not eliminates or reduce them just because they are local. Accountability is better, but it will make politics more petty and personal. Talk to people on reserves, good and bad ones, and find out for yourself what handling everything in the community actually entails, including the politics, instead of an idealistic version.
It will mean phone calls late Saturday night because you are the financial officer, two doors away, and the water tastes funny after eating a box of crackers. Or someone yelling outside your house at four in the morning because the pothole reported eight hours ago hasn't been fixed yet, and you're the one that arranged the road repair contract two years ago, Yeah, I've worked in municipalities and talked with people living on reserves and these things are commonplace, and pretty minor compared to some of the shit that has to be dealt with.
I'm not saying it's insurmountable, the same as getting a community-minded spirit, I'm just saying that its going against the flow and it's a lot more work for a small amount of benefit.
People want convenience. Libertarianism isn't convenient. It's hard work in exchange for more control. That will appeal to some, but not the majority of people. In Canada, the politicians do best that you never hear from. People want the things that keep the country running to happen invisibly in the background. But, you probably already know it's an uphill battle.

Thanks for sharing your thoughts.