The benefit of measuring a mesolensing event is that the mass of the lens can be determined from the light curve. This is especially interesting for single stars where no independent mass estimate is possible.
Brown dwarfs like Luhman’s Dwarf are especially interesting targets for mesolensing because they are dark at many wavelengths, and so permit measurement of the mesolensing by background objects without worries about contamination from lens light.
Stars and brown dwarfs are not typically bright radio sources, although they can have strong episodic emission. In principle, VLBI astrometry has the angular accuracy and precision to detect astrometric displacements of these sources (resolution of 0.5 mas), as does ALMA at its highest frequencies (barely resolution 6.5 mas at 675 GHz). The latter has the collecting area to make such observations feasible, even for faint galaxies, but probably not for distant stars, which are typically undetected in the radio.
Brown dwarfs are optically nearly black, so even faint background objects could be used as sources. In this case, the astrometric displacement would be inaccessible, so the entirety of the effect would be via magnification.