(This felt like a too long comment so I post it as an answer)
The basic equations are usually expressed in geometrized units so it's no problem to rescale the mass and get the respective quantities (this can really be obtained even from the original article). Then you have the required magnetic field ∼L1/2 with the output luminosity and ∼M−1 with the black-hole mass.
For supermassive black holes you usually get ∼0.01T magnetic fields but for the tiny black hole with mass ∼10−23 times that of the supermassive to even flicker, I fear the magnetic fields would have to be monstrous. Additionally, I do not really see what sense does it make to study the effect in concrete situations without having a handle on the external supporting current (aka the accretion disc).