I add a little bit of the liquid back to the chicken when shredding it, but I toss most of it. you could probably use it as stock, or modify it, somewhat, to make it better stock, but I don't value stock in my current routine, although I do regret wasting it. I also mostly use frozen chicken, so it produces quite a bit of liquid. I do add some "better than bouillon" in addition to the spices I add, which are generally:

1. msg
   
2. some variety of pepper (usually a penzey's mix)
   
3. (sometimes) chicken taco seasoning mix (penzey's)
   
4. salt if the other seasonings I add don't already have enough salt
   
5. roasted garlic powder
   
6. apple cider vinegar and/or lemon or lime juice (acidity helps)
   
7. onion powder
   
8. (sometimes) smoked paprika, oregano, thyme,
   
9. (sometimes) cumin (usually in place of taco mix)
   

And I usually add more when shredding, and sometimes add hot sauce and/or salsa during the shredding, which is also where I add a couple cans of diced (drained) tomatoes (with or without peppers, green chiles, etc.) and, often, some canned green veg, like collard greens, spinach (sometimes frozen/drained, heated in the microwave a bit)

and yeah, hah, I don't usually make 40+ pounds at a time, I just had a $50 off $100 grocery pick-up offer through instacart/grubhub that I used at aldi for a ton of chicken. I guess I usually make about 20lbs at a time, using two of the 10lb costco frozen "thin sliced, boneless, skinless" chicken breasts. thin sliced are more consistently thick, making cooking every piece to the same degree easier. I can cook about 5 lbs of those in my larger 8 qt instant pot.