Many sources allow for fantails and moors to be kept in ponds. They were originally bred to be seen and appreciated from above. Many people keep fancies outdoors successfully. However, water quality must be very scrupulously maintained as the fancier fins can get congested if the water isn't great.
I have seen a huge red-cap oranda being kept in a beautiful garden pond in Cambridge, MA -- this pond is 6' deep and has a nice aeration/filtration setup. The remainder of the fish in this pond are comets or fry from the oranda X comets. From what I understand, some of the fish are overwintered outside while others come in. I can only assume the oranda comes inside. They're not really suggested as pond fish because of the wen. I have two of those oranda X comet crosses -- one is over 12" the other is 9" -- they both have a smallish head and hint of a wen, somewhat fuller comet shape and very full, showy single caudal fins. The current owner told me the pond is about 10 yrs old. Considering the size of this fish and it's fry, it may be an original inhabitant.
Fancies don't usually fare well with single tailed goldfish because they just can't typically compete with their faster companions. I think the ones who most frequently fare well are those in more natural ponds with plenty of grazing opportunities.
Why not have a small pond with just fantails? In a 170 gallon pond, not more than 2' deep, a small group of fantails would be really striking. I used to keep a couple of my fantails in a 45 gallon 'pop-up pond' and loved the effect (my retrievers were drawn to the nice 'wading pool', so I moved them into a 46 bowfront before anything untoward happened)
In an area that gets snow, imo, 1.5' - 2' is not deep enough to overwinter and they should be brought in. Rubbermaid stock tanks are awesome for overwintering and can be bought cheaply enough at feed stores in up to 300 gallon capacities. The pond filter can be brought in also to use overwinter, so the bacterial colonies won't need to be re-established in the Fall and then again come Spring. The smaller rubbermaid containers work well too, but the stock tanks are tougher and usually cheaper gallon for gallon.
BTW, caution needs to be the word when it comes to mixing plecos and goldfish. In most cases, you're better off not combining them imo. I've done it but it was a matter of expediency for the _short term_ and the plec was very well fed on plenty of garden surplus. A goldfish is no match for a pleco if a problem arises. Goldies love nibbling algae. Algae blooms can be avoided or managed in other ways than using a pleco.