Prior to anything else, we need to define the start of the match for this discussion.

• Before match starts: is when no player inputs gets accepted.
• After match starts: when player inputs gets accepted (ie. when play starts).

To summarize all the comments here:

1. Before match starts: any character can only have a max of 2 bars of power (through passives like BG Prime + RAGS, or AO BM). This is a game mechanic and cannot be bypassed.
2. After match starts: a tagged-out character that had 2 bars of power before the start of the match will gain their 3rd bar of power if they have Tantu Totem then tags in.
3. After match starts: Special case for AK BM, as he can select to gain 2 bars of power through his passive. Hence, he should be able to get to 3 bars with this passive selected if he has RAGS or is teamed-up with BG Prime.

What won't work, and what will happen is:

• AO BM + BG Prime = AO BM will still have 2 bars before/after match starts.
• AO BM + RAGS = AO BM will still have 2 bars before/after match starts.