there are many systems like that. its fine to have water sitting in buckets as long as there is an air pump in there (in any dwc). the rdwc systems dont let water sit in the buckets, but are connected by tubes at the bottom of the buckets, and are fed by tubes at the top of the bucket, and generally all flow into a res bucket, with the water pump sending it back out from here. easy to make. i probably wouldnt buy one cause they are hella expensive.
temps should be less of a problem in this kind of system than an ordinary dwc with no circulation.