Streams aren't that difficult to do, they do require some extra planning though. Like if you are not using 1 continuous piece you need to figure out your overlap, easiest to do a fall right at that point. But adding a stream later is also very easy.
Just to give you an idea of costs, my main pond is about 3000g (drawing a complete blank on dimensions though lol but about the upper size you are thinking), the stream is about 30ft long, the pit/skimmer/pump area is 9'x7'x4.5', the bog is 10'x3'x2' and we used about 22 tons of the cheapest stone available to us. I reused a lot of materials like barrels, the bog frame, some rocks and got big discount on equipment like the waterfall box, pumps and underlayment. Estimated cost including arrounding landscape is close to $15k. No labor or equipment costs. A few grand was for the rocks and you probably can get rocks cheaper there.
I live in central NJ. We do have raccoons and herons, the herons fly over every day but never stop as far as we know (someone is in the yard nearly all day every day though). I built my walls straight to deal with that and up until a few weeks ago I never had any possible predation. 2 fish have gone missing and I can't rule out predators but they are females and could be hiding in the cave OR jumped out running from males and were then eaten. *shrug* You have the right ideas (making the sides steep, no pots or steps that they can stand on, hiding spots) and I agree netting is horrible and I will do anything to avoid that. In your area wildlife may be more of an issue though. You do have a lot of tree cover so heron may not even be able to land. Bears....I have seen bears in ponds (moose even!) Just hope they don't come?
Properly installing a good skimming system will take care of tree debris. Underlayment will hinder tree roots, protecting the liner and will keep the walls sturdier.
The water table issue I have no experience with so I don't want to speak to that. Knowing what a big concern that is for you I will recommend a different forum where I know there are some canadian pond keepers (but in like 3a conditions) and lots of experienced keepers.
Garden Pond Forum I do know from research that the water level in the ground would have to get pretty high before it would be strong enough to push the liner up cause the water IN the pond does hold it back. I worry more about it eroding the walls away.
Equipment can be hidden so easily. Depends what equipment you go with but examples are...a skimmer and waterfall box setup is hidden with fake rock tops, done. Barrels, trickle towers, etc. you can build mini houses that match your back houses or make them look like fish shacks. Since you are handy making your own fake rocks can be fun and give you complete versatility to hide your unique equipment. My skimmer and pump vault covers for example and I will be making more soon to cover other areas. If you go with a gravity fed system and have a big hole where the equipment is you can make the cover look like a dock. Worry about what equipment you want to use and we can find a way to hide it.
Hidden equipment was important to me too!
Runoff is avoided by making sure your pond is not in the lowest point. If it is just build the area up a bit, doesn't take much.
Excuse all my typos please.