Keep in mind that being MVPG flying partners won't give you any benefits besides mileage bonus, as I assume as UA G flying TATL you at least enjoyed the lounges.

If that is OK for you, then why not? I matched from UA G to AS MVPG last Oct, and requalified this year mainly on CX's TPAC flights. I try to fly AS metal as much as possible when flying domestically though, as AS is treating me well (like 11/12 upgrade rate well)