I am using Hydrofarm's EMSYS which has a drain tube. Directions say take the plug out of tube and drain into a bucket. Refill through the planters. Don't know if that is going to take a lond time, haven't gotten there yet! But I would think, no matter what system you're gonna use, if it doesn't have a drain, you could add one yourself. Even tho I'm a Noob, seems like common sense that you don't want to move the plants every time you changes the nutes! Hope that helps a little! I'm learning as I go, so I could be wrong.
ill give you guys an idea of what is possible... Aerogarden DWC is not too shabby, but its way too much work. id never do another grow unless it was only 1 plant