In my opinion this should be as robust as possible to give you options. My system has 2 different configurations....
A) A Renew continuous water changing system
B) The ability to mix 55 gallons and bring it on-line after draining 55 gallons of existing tank water
C) The ability to draw buckets of RO/DI water or Saltwater
You run the system in either configuration (but not both) but the beauty is you never have to touch a bucket. In addition, my sink has it's own RO/DI spiget on the sink for cleaning the test vials. We are not up and running with this sytem yet. However, I designed the system to be as automated or as manual as I need. I plan on running it 99% of the time using the Renew water changing system.
Here are some pics.... It's hard to photograph because it's in a fish room and located behind the 400 gallon display. Here are my best attempts at pics....