Hi HRHAndrew,
Before I attempt to help you, I have some questions for you.
What are your aims?
Do you want status or going for top tier with other airlines?
Do you want as many miles as possible, shortest route possible or like to venture off to see other places in the time you have spare?
You do realise the value of AONEX's are diminishing with the phasing out of First class on many routes and airlines. It may be worth considering a Business Class RTW product. There are many options available with varying RTW products with oneworld.