Next-generation solar spectrographs increasingly record dense wavelength windows in which tens to hundreds of spectral lines are sampled at each spatial location and time step. This expands the scope for multi-line, multi-height diagnostics of magnetohydrodynamic (MHD) motions, but also raises a practical challenge: deriving stable line-core intensity and line-of-sight (LOS) velocity time series when profiles evolve rapidly, become asymmetric, blend, or develop multi-lobed cores. Common fast est