Check out the new plastic (PEX actually) water lines. They are easier to use, have less elbows for greater flow, are a good DIY'er project and cost way less than copper. Run a 1/2" line from your water main and as close to the water heater as you can to each new fixture. This way you will not get scalded if someone flushes the toilet. So for example you will have 3 cold water lines and 2 hot water lines for a tub/shower combo, Lav and toilet. 5 lines will still cost you less than by doing a 3/4" copper cold and hot water supply.