want to join a G5 conference with some good teams but some really bad teams instead of just inviting the good teams from that conference and remaining an autonomous conference?"

Its a no brainer, unless a P5 offers them a spot the BIG12 teams should remain together and invite some combo of: BYU, Cinci, BSU, UCF, Houston, etc.

It seems like BIG12 teams are in a wait and see position to see if the PAC12/ACC/BIG10 swoops in to save them (i doubt they do, who makes it worth it?) rather than being proactive and actually stabilizing their conference.

No combination of the available expansion combos make up for the lose of UT and OU but it is a LOT better than joining the AAC en masse and losing their autonomous status.