I have never tried upgrading a console stereo's cartridge. But if I were to do so, I think Grado would be my absolute last choice. At best, I'd be cautious. I've had experience with Grado on modern turntables. I like some things about the cartridges. Unfortunately, I (and others) have found them to be temperamental at times. Tracking isn't particularly good. And they can pick up hum from turntable motors (this varies on motor) and AC transformers in amplifiers. For a console stereo, I'd want something that "just works" with a minimum of fuss. Although the final decision would, of course, hinge entirely on the circumstances of the particular project (changer in question, my plans for how it will be used, etc).
Actually, as I think of it now, the cartridge I'd be tempted to try would be the Shure M44. It's sold as a DJ model. But the cartridge body was, back in the 60s, a home model--and one that was, for a short period, top of the line. How well it would work depends on the particular changer. But I'm pretty sure that my parents had Shure M44 upgrade to their low-end changer, and from my memory, it worked just fine there.