Dave, I like a thinking man. Given that a tank setup is a big commitment, it's great you've thought it out. I've really never given harvesting practices much thought, but you do have a valid thought process. My biggest drawbacks were the fears you've expressed - increased maintenance, higher investment costs, higher priced inhabitants, and possible sudden failure. I've always been intrigued by the saltwater realm. A lot of them can resemble alien-like worlds and can have tons of unique inhabitants. With that, I'd have to say my favorite part about freshwater tanks is the naturalism they afford. I know I'd have to put forth a lot of effort and probably money to get a salty to function as close as possible to a natural environment. Even then, I don't see it ever being an aquarium that could take of itself. My tanks have been taking care of themselves for years. I change 50% water, wipe down any algae starting to show, clean the power canister filters, and remove any overgrown plants about every 2-3 months. Other than that a little daily feeding and maybe a little water addition to top them off weekly. They truly take care of themselves, finding the larger the tank, the more robust they are. If I want to get slack and put off some duties, I have no worries anything will crash. I can leave for the weekend (or the week) and return knowing everything is as good as it was when I left. If the power goes out for a day or two, everything is just fine. I like the luxury of using water right out of the tap with a little Prime and everyone goes about their business without the slightest inconvenience. Finally, I have the luxury of a nice aquarium downtown if I want to see salties in action.
Dave, try
www.aquabid.com for plenty of freshwater variety. Most times you know if they're wild-caught, farmed, or raised by hobbyist.
Good luck on your adventure!