I have a pretty strong argument for b3. All table is master, so sensibility can be high, so that seem to work.
It's because 5 is stronger then blue on chouchoutuba.
Imagine ghost clue 5 to chochoutuba. What happen next?
5 call for b3+b4+b5.
First, let's look at Sammy's hand. He sees m1+m2+b4 on Tomi's hand, so he only need to play b3. So he plays k5.
Then we got others problems in between, but let's skip them for now. Others players will assume b3 is on Sammy, and will not interfere.
Then it's Sammy's turn again, and he plays b3.
Then Tomi will play m1+m2+b4 and chouchoutuba will play b5.
So outside of that problem, that work.
So now, when ghost decide to clue blue instead of 5 and do in purpose a worst clue by not getting m1+m2, that should call for something else => b3.
Now let's talk about that problem. Sammy plays k5, and now it's Chouchoutuba's turn. Tomi's hand is m1-m2-b4-k1.
Chouchoutuba can clue 1 to Tomi though, that will save k1, that should change the position of b4, and I think that should get m1 played?
I think if you don't care about complexity, the reasonning is really strong, I would love for you to break it or try to break it.
Now if you care about complexity, which you should, it's a risk of losing an unique b3 and that desynchronise the team. The clue is about 3 others players, so 3 players need to understand it. I don't like it.