Depends on your definition of better.
What ffp will you be crediting the miles to?
What is your status at the start of the RTW ?
Are you trying to get or retain status ?

Yours is a valid intinerary, however A (first) will not be available on many routes. eg syd-per-adl-akl-adl
1: CAI-LHR: 1st of 4 (Europe)
2: LHR-SYD: intercontinental
3: SYD-PER: 1st of 4 (Southwest Pacific)
4: PER-ADL: 2nd of 4 (Southwest Pacific)
5: ADL-AKL: 3rd of 4 (Southwest Pacific)
6: AKL-ADL: 4th of 4 (Southwest Pacific)
7: SYD-HKG: intercontinental
8: HKG-JFK: intercontinental
9: JFK-SCL: intercontinental
10: SCL-EZE: 1st of 4 (South America)
11: EZE-GRU: 2nd of 4 (South America)
12: GRU-JFK: intercontinental
13: JFK-BGI: 1st of 6 (North America)
14: BGI-JFK: 2nd of 6 (North America)
15: JFK-MIA: 3rd of 6 (North America)
16: MIA-POS: 4th of 6 (North America)
17: POS-MIA: 5th of 6 (North America)
18: MIA-LAX: 1st of 1 (North America Transcon)
*18: MIA-LAX: 6th of 6 (North America)
19: LAX-LHR: intercontinental
20: LHR-DXB: 2nd of 4 (Europe)
Congratulations!! Valid itinerary!!! - (64253 miles)