Status match or challenge.
Has been discussed many times. Get AS or DL to match your AC status, and then do a UA challenge

You can always accumulate UA and use your AC benefits (boarding, lounge) until you get gold on UA.

The new earning scheme will severely affect your mileage earnings on UA though. A $1000 ticket to SIN will only earn 5000 miles at first. That will hurt, on a roundtrip of over 20000 miles.

Status mileage hasnt changed, and you will indeed be 1K after 5 trips to SIN.

So what do you want, status benefits? guaranteed economy plus? redeemable miles?

Once 1K, you will get 6 upgrades that you can use on W fares or higher. (3 RTs)