I'm not that good with the simulators, but I'll try for this one because it's actually really interesting.
I'll edit info into this post if I figure anything out.
So for starters, in Noble Brigand vs BMU you don't care about terminal collisions at all. For a short test, I took the computer-generated bot and only changed the number of Noble Brigands it buys. No change to any other buy rules. And it turns out the optimal amount of Noble Brigands is 9. Yeah, 9! It turns out that the repeated attacks from buying + playing Noble Brigand is just that good against BM.
I'm a little wary of doing a similar strategy to find the best NB mirror bot, because Province buying is determined on $ in the deck, and with NB out tracking that is a bit of a nightmare.