>>51648977Update:
After staying up 'til 2 in the morning burning through GBL sets, I checked my Metagross lineup and realized one of the remaining Metagross had a higher combat power than my sixth one, so I decided to burn through 700k stardust to get that one to lvl. 40 and my top 3 to lvl. 45 (saving 144+ candy XL for if I find a better Shadow Beldum before Mega Glalie gets released). Now I'm fairly certain that I'll be able to solo Mega Glalie whenever it comes out, regardless of weather, but my odds against Mega Aerodactyl and Mega Altaria in snow are still rough.