I somewhat agree, bm wont lose to Wano/SN/SH.
As she said that she doesnt have enough soul & she made several homies & she straight away asked Kaido'poneglyph location. It feels she is ready to back stab Kaido (weakened by 5 SN, of course the later are weakened too) whenever her homies get Kaido's poneglyph location. thats why she left marco to see whether kaidos already weakened.
the matter of BM soul, i'm afraid that the story somewhat like Madara takes Obito rinnegan "its mine to begin with". BM takes Kaidou soul:"you have to pay me back, as i have made you the strongest creature".
but then again, if there are +- 170 chapters left, BM should be beaten/capture at wano. That leaves the only one option, An admiral with at least 10 battleships (plus either gion/momousagi & or (Rocks-related - garp insist to accompany like sengoku at Dresrosa) takes her.