Hi Flyertalk people, I am a SQ Krisflyer Gold but expect travel frequency to go down (to about 40K miles per year)

So I want to switch to OZ to get fast *A Gold status. For now, I have quite some SQ miles but no OZ miles.

I am checking options for an upcoming return flight JFK-SIN in fare class B/Y. I can basically take any of BR, OZ, SQ, and UA.

Here is the question. If I want to upgrade my flight from Y to J, can I use SQ miles to upgrade a, say, BR ticket, and then credit it to OZ? I know this involves too many parties and that any part goes wrong can ruin the trip. But it will help me a lot to improve flight experience while getting the miles for my status!

Thoughts? Advice?