Supply line design and size for 2nd bathroom

I am adding a new bathroom in my basement directly below the main floor bathroom. After looking at Terry's chart on supply line sizes, it looks like branching off the main floor bathroom's 1/2" lines will lead to problems. I'm wondering if my supply system will properly support the new bathroom (toilet, lav, shower w/ body jets).

I have 3/4" leaving my water meter which then feeds (in order): clothes washer, 2 hose bibs, 1/2" line to main floor bath/shower lav toilet. Then the 3/4' reduces to 1/2" which feeds the hot water tank, and then the kitchen sink/dishwasher.

The hot water then feeds (in order): kitchen sink/dishwasher, clothes washer, main floor tub/shower, lav.

I was going to just tap off the 1/2" lines going to the main floor bathroom to feed the new bathroom but now I'm wondering if I should run a new 1/2" back to the 3/4" supply instead. I don't see much alternative but to run the hot water off the existing supply.

Any advice or comments would really be appreciated.

Home run it

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.

Thanks for the input. Just so I understand, I should run 3 separate lines from the 3/4" supply and 2 separate lines from the hot water supply line close to the HW tank? Sound right?