Your best bet is to take a look over at the oneworld forum to get advice on RTW routing, they'll be best placed to assist you. The biggest issue you'll face first is a maximum of 20 segments allowed in total on any oneworld RTW ticket (even if the various continents have a higher total if added up, the maximum allowed is 20).
Also, if you want to go through Fiji, the only way you can do that is on the Global Explorer, which has a maximum of 39,000 miles in economy, or 34,000 miles in Business or First. You won't be able to do it on the continent based oneworld Explorer.