Should work. If you want to add mores miles, and are flexible and have the time, I'd add a few longer segments in Europe/Middle-East such as LHR-DXB-LHR and LHR-HEL-LHR, an additional segment such as MEL-PER or even replace SYD-OOL-ADL-MEL-SIN with SYD-AKL-MEL-ADL-PER-SIN. Like wise, you can do longer trips in Asia such as replacing HKG-ICN-HKG with HKG-DEL/BOM-HKG.

Not sure how many sectors you're allowed in N. Am. but LGW-DFW-BOSwould be nice.

Downgrades should only come if you are standing by for D inventory and it doesn't clear.