What does the BO really want?????

[Rellik]

BO is merely another dangerous organisation like mobs, just at a whole new level. And any gangs would want is money and power.

So basically this includes immortality and stuffs like that.

[Shin-chan]

Ai said it wasn't zombies, which doesn't fully discount raising the dead but that seems unlikely even with the age regression in this series.

Conan also found "Shiho Miyano" (and then conveniently got distracted from thinking about it too much) in the records of the raffle for the immortality arrows in the mermaid case, which is more evidence of the organisation being interested in immortality.