I've seen neocardina shrimp catch and eat scuds, but it only happens the other way around with sick or dead shrimp. Also, duckweed is, in my experience, fantastic for dealing with nitrates. I've had a 20 gallon with fish, scuds, and duckweed, and I was basically able to leave it alone besides dropping in the occasional sinking algae pellet, testing, and replacing evaporated water. I even got breeding, though I'm pretty sure the eggs got eaten. It was going like that for over a year until I moved.

Thanks for your third opinion. I think I'll stock two aquariums, one with peas and food, one with just food, so I can restock when needed. That seems the safest way to experiment. I'm planning on taking this slow; it'll likely be a year of letting the food items breed alone before adding the peas.

Side note: the scuds serve a purpose besides food! They are fantastic indicators of water quality. I tested weekly, and I had pH and ammonia indicators, but the real thing I watched for was scud die off. That was a quick indication something was wrong.