AC's Aeroplan may fit your needs. Not a lot of difference doing SYD-YVR-SFO than SYD-AKL-SFO after all. Whilst they don't participate in the * Upgrades scheme yet, they only want 35K Q miles per year for *G equivalent and the upgrade certs, lounge access etc that comes with that status. Their hard product has improved out of sight with the recent refurbishment or newer equipment being used on their fleet worldwide. Soft product is as always hit and miss.
My reasoning is based on thinking if you do have a bad year where all you actually do end up flying is the 2 SYD-SFO returns, then that's just under their 35K threshold level required and any other tiny segment anywhere else on * will get you over and maintain your status.

Then again, it's not too much longer, relatively speaking, before UA gets it upgrades rolled out. Maybe fly the other 2 options (AC/NZ) for the status/miles into M+ as a short term measure until M+/UA appeals once more with it's new hard product.

Another thought - if you go elsewhere and struggle for *G, whilst it won't help you as far as upgrades go, AC does offer a seperate tier of Maple Leaf Lounge membership (Called Worldwide or similar) that gets you access to a heap of Star lounges worldwide when flying a Star carrier from that airport on the day.

I also agree with KF. The hype around the Alliance Upgrade scheme is way more generous than the actual scheme itself, given that you can only upgrade out of the highest cabin fares possible and at redemption levels that aren't exactly the best.