If you don't like the duties of the federal government spelled out in the constitution - amend it. Don't ignore it.

Actually - you're really on point. Let's take a look at the current government.

Roads - should be privatized ($x/mile driven)

Yes - we have this. They are called toll roads - see NJ turn pike, and may tunnels and bridges. The person using it pays, great idea. Honestly, the gas tax is also a roads usage based tax (hence the discount for farm diesel)

Water supply - should be privatized ($x/gallon taken into the house)

I'm sorry - you don't pay a water utility based on consumption now? Where do you live?

Sewage treatment - should be privatized ($x/gallon taken out of the house)

Check - my sewer bill is on the same bill as water. And my parents have a well and septic tank. No fee for them, because they are "off the grid" - More common than you think.

Police - should be privatized ($x/call to 911 etc)

Actually, that's a damn good idea if you bill them after the service. Police do this now in some states with the "accident fee" - call the cops to the scene of a car accident and you get a bill for 500 dollars.

Fire department - should be privatized ($x upfront to have your fire put out, but the neighbors can chip in so their houses won't be next)

I'm sorry - you've never heard of a fire department fee? Check your homeowners policy - your insurance company pays it for you. Many areas are still "subscription" - ever given money to a volunteer fire department? Yup - that's what you're paying for.

Army - should be privatized (don't want that North Korean missile [popsci.com] landing in your backyard? I hope you have the money to pay for it)

Actually national defense is one of the few responsibilities of a federal government - check the constitution when you get pouncing on it.

Schools - should be privatized ($x/day of school, and of course for missing school, turning in homework, missing homework etc)

Correct - I went to private school and so did my parents. Their parents worked hard to put 8 kids into catholic school. My grandparents went to catholic school too, they remember tuition cards that the nun stamped every week.

Power (including lease of the lines that feed your house) - should be privatized

Um - it is. http://en.wikipedia.org/wiki/Maryland_Electric_Deregulation

Even before that I paid power bills to a private utility.

Street lighting - should be privatized (why not charge neighborhoods for the privilege of light?)

I see you've never gotten a bill from a homeowners association? What do you think that pays for?

Garbage collection - should be privatized ($x/lbs of garbage, extra charges if you don't sort everything perfectly)

Yup - we have to pay for that too, as I recall it's $100 every three months for the privilege of BFI to pick up my two cans. No charge for recyclables though.

Ambulance - should be privatized (got mugged, wallet and ID stolen, head smashed in? Too bad - if you don't have the cash or picture ID to show that you're covered, the EMTs won't help you)

I see you haven't taken a ride in one lately. A few weeks after, look out for a bill of about $1000.