On the fish, I would only keep the zebra danios, weather loaches and plecos for a colder water setup.
I don't know why you can't just keep the water in the tropical range because white clouds can take the warmer water. White clouds if kept in warmer water can be kept will all the fish above with little problems. The only fish that may cause an issue would be the gouramis and shark if they are big enough to eat the minnows. But if they are being kept with the danios, zebra danios are in the same size relation as white clouds.
As for plants, I know Amazon swords need warmer water. Not sure on the others.