I bought a 40g plastic jug and strapped it to a dolly. I threw in a Koralia powerhead, heater, and Mag 1 pump. They all plug into a 4 switch DJ power strip for easy on/off. I mix my salt water in the jug and use the mag drive to fill the tank back up.
Unfortunately, I'm still lugging 5g buckets of old tank water, but refilling the tank is a lot easier.
If you mimic this, don't fill the 40g jug to the top. 20-25g the most you'll want to try to cart around.
This model could be modified to avoid hauling water. You'd just have to run plumbing from the reservoir tank to your sump, and find some way to pull water from the tank to a drain. It should be pretty easy if you have a tank room or direct access to plumbing behind your tank.