As a fish keeper for over 40 years. I do care about the welfare of the fish. I can come in every weekend for about an hour or so to change water--job not too far from home. Heater is not an option and there are no "scheduled" power outages over weekend.
So cold water it is then. White cloud minnows, barbs and some species of loach come to mind as common cold water fish that you could get at a pet store. Your options may open up if you have some hip waders and a net.
1) White clouds are OK as an option, with some other fish.
2) What barbs and loaches are cold water??
3) NO hip waders. I buy fish, no good at catching them in streams.
Some of the cobitidae family can work for loach. Dojo loach would be the most common, and they can handle places where it gets below freezing in the winter. I'm not too familiar with the others; you may want to poke at the other Misgurnus sp. with some reading.
I was just doing some reading on zebra danio's, and they can possibly handle water of that temperature. I know they live in water that gets down to mid-50's at times. I've seen guppies and plattys endure some cold temperatures over long periods of time, though I'm not sure how it impacted them. Gold/green and rosy barbs may work out as well. This is all a list off the top of my head, and I'm sure there are a number of others that you can get in there. It might be worth reading up on the habitats of the fish that interest you; some preffer different params than others. Most of them are pretty tough fish IME though.
You have quite a wide array of options if your boss is open to smaller fish than goldfish. You mentioned he wanted large fish, which is why I said your proposed setup was impossible.
The problem of doing water changes and your boss's aversion to buckets or hoses snaking to the sink still seems like a large problem to me, but if you think there's a solution to that you could certainly have a viable setup.