LVM self-calibration

I read and commented on some documents today related to the calibration of the Local Volume Mapper part of the SDSS-V family of projects. The project is an intensity-mapping project to observe the interstellar medium in the Milky Way and nearby galaxies, using one spectrograph but many different telescopes (with different apertures). It's clever! The question is: Does this project need calibration telescopes in addition to the science telescope? My position is that they don't. Well, calibration telescopes might be very useful for debugging things and understanding things! But at the end of the day, calibration will be self-calibration I bet. I'm offering very good odds.

One point is the following: When you have an imager or a spectrographic imager, you have to calibrate so that every exposure has calibration consistent with every other exposure, and every pixel has calibration consistent with every other pixel. Good! Now imagine you introduce a calibration telescope. Now you have to do the same for the calibration system, and you have to understand the cross-calibration between the systems (science and calibration). So it greatly increases the difficulty of the task, introduces new variables, and (usually) reduces precision of the final results. The self-consistency of the science data (provided that it is properly taken) is always the strongest constraint on calibration. See, for example, Planck, WMAP, SDSS, PanSTARRS, and so on.