Gigs and juggling are only a thing if you have moonlighting, true. On the other hand, it's perfectly reasonable for the MC to simply give a dude the moonlighting move if he's done the work of setting up a couple of regular gigs, right?
I believe operators typically have more gigs than juggling, don't they? They start with 3 gigs? Plus an obligation gig? And still just 2-juggling. People who pick up "moonlighting and 2 gigs" probably won't run into that, but if you have more gigs than juggling you just pick which ones you're going to work. Juggling just shows how many gigs you can have going at a time.
And you can work fewer gigs than your juggling, right? Gigs left on the table because your juggling is lower than your number of known gigs work just the same as gigs that you simply chose not to work because you didn't want to work gigs up to your full juggling.
If you truly lose a gig, you could end up having more juggling than gigs, technically. But I think usually you wouldn't lose the gig, but just get shut out of it and need to find a new place to work it (and until then, you just can't choose that gig when you're picking which gigs to work).
Like, if you were in compound defense, you still know how to do that even if the compound is a smoking ruin ... if you find someone else with a nice compound that needs defending, maybe you can sign up with them and start working that gig again.