Plumbing the tanks would be kinda cool as long as you have ball valves to cut the supply. But then you have a QT hard plumbed to the DT, weird. Anyway, I use my method because it eliminates another source of stress (water parameter stress) from what the fish is experiencing. I think a big part of nursing a sick fish back to health is to eliminate as many stress factors as possible. With using the DT initially, you already have all perameters in place in the DT --> QT transfer. It allows immediate hospitalization if need be and keeps the focus on medication/observation than on worrying about acclimation and parameters. If you break it down to basics, you have to get the fish out of the DT before you can do anything else and if you have to get it out in a hurry why wait for a half hour to get your salt probably mix. Where as in that same half hour you can get your QT going, have a salt batch mixing, your getting the fish to the QT, observe and treat if necessary and when your batch is mixed, mind you its not aged at this point of course, you now have your top off water for the DT and maybe some extra left over you do a partial change to the QT. Even if the QT has brand new water in it the pathogens are going to run there course anyway.