Really, really bad idea. The boat would wallow through the water, and would not be stiff enough running upwind. Probably dangerous to sail.
It takes about 20 seconds to tack a boat. How long do you think it will take to pump water from one tank to the other? All the time that is happening, the water is on the downhill side of the boat (so your centrifugal pump is pushing uphill, so nowhere near its rating), leaving your rail buried. By the time the ballast is in the right spot, it is probably time to tack again.
And how long do you think your batteries will last running the pump? That is a lot of juice.
Putting the water high enough to make a difference makes your boat intrinsically unstable. While the water is being transferred (both tanks partially full), there will be a lot of free surface, so a lot of sloshing, making your boat even more unstable in the waves.
Small sailboats generally don't use an active water ballasting system (usually only used for ocean going boats that are going to be on a long tack for a long time, so it is worth going through the effort of pumping water to the uphill side). Look at the MacGregor 26; water ballast tanks are down low, where they really don't provide any righting moment until the boat is almost on its side. And the hull is designed for it, with the tanks in the exact right spot.
You don't understand the point of raiding? Its a type of racing that involves small light boats, light enough to drag up on the beach and over sand bars
I don't think you will be dragging a Cal 21 over sand bars by hand, even without the 360# swing keel.... what is left weighs at least 800#... You want to go raiding, go for a small dinghy that can be portaged by two people easily.