[jeff5may]

Yes, it would work. How well depends on how much you "Tim Taylor" it.

If you let the outdoor unit do the sucking, this drags down the airflow thru your heat exchangers. If you add enough water pump to the radiator, you might break even. If the outdoor unit has a variable speed fan, it will work against the radiator. I.e. more water>warmer air>fan slows down>same heat extracted.

If you add a fan, both heat exchangers will have more air going thru them. If you pump enough water and air, you might break even. Same effect as above.

During awful weather, the radiator will help the most. More delta T from well water temperature = more capacity for help.

In comparison, spraying a small fraction of the water you would normally pump through the radiator directly on your dx coil will have the effect of a nitrous oxide boost on your heat pump. Just a little spray has lots of energy in it. Only this way, the fan cannot react fast enough to help. I.e. spray water>coil defrosts and warms>massive BTU surge>compressor and/or metering valve must slow the flow to avoid overheat condition. If no over heat condition exists, unit runs balls out until satisfied.

Either way will work. Try it both ways. Just don't drown your new unit.