cool project and super cool blog/website
Makes me want to start over at about 18, and travel more than I did, but no complaints, life is good.
The construction trades used to use copper for shower pans and other waterproofing before synthetic rubber and plastic products were readily available at a lower cost. Since this is going to be your full time custom home go for the copper countertops and if youre so inclined either hand hammer seamless sinks or bend and solder them to your dimensions. The determining factor in how you use the copper is its thickness, if its thin you will need to build a supporting structure and use it for cladding like formica on a countertop, if its heavy enough to be structural either have a sheetmetal shop break/bend it to your dimensions or try clamping it to the edge of your bench between some stout angle iron and slowly working it with a hammer and block of wood or another angle clamped to the edge you want to bend.
To hammer a sink, I'm thinking round bottom lav type sink, make a round faced wooden mallet and either a wooden form or a box/bag full of sand and start hammering away most metal will start to harden as you wok it you may have to heat anneal it to keep it workable.
Google for information on working sheetmetal / copper and buy a good book on it.
Copper will take on it's own life once it is installed, the finish will turn into a history book of it's own if you leave the everyday stains and marks instead of keeping it polished, either way it's going to look real good.