Seasonal Solar Attic Water Heating...

Ive read that many homes in Florida keep the water heater in the attic, thus hettinh a noost from the ambient temperature.
It freezes here, so this wouldn't be a good set up year round.
Instead Im considering a three way junction in the cold water supply line.
One branch would travel out the basement  and up the southern facing wall of the house.
When it reaches the attic,  it would connect to a de insulated 40 gallon water tank that
That tank would be painted black and sit inside an insulated box, behind a southern facing window.
From the tank, another line would return to the basement, and feed into the cold water supply of the has water heater via a second threeway junction.

During cold months, the solar section of pipes and tanks would be drained.

Depending on where I would need to use copper, i coukd do this fairly cheaply.

Does this seem like it would be worth thr effort?

I'm liking the idea of harvesting attic heat in the summer.  Do you currently have a South facing window in your attic?  

My attic gets quite hot just due to the shingles collecting heat.  I wonder if you could get the same effect by coiling a long length of 3/4" PEX tubing in the attic.  So the three way tee would lead from the basement up to the attic.  Then it would just transition to the PEX and coil around for a while.  Then it heads down to the water heater inlet.  Whenever hot water is used, the tank would be supplied with fairly toasty water until that coil in the attic has been refilled with cold water.  If that supply isn't enough, a tank could do the same thing but be sure that you put is somewhere that can handle the weight.  40 gallons x 8 lb/gal = 320 lbs.

The coil is a great idea,though getting it all to drain might be difficult.
Perhaps blow it out with compressed air?
Theres no window right now, but it might not be needed.
In fact, the window and insulated box is pretty much a batch solar heater.
My goal is a simular effect with simpler infrastructure,so I'm ditching the window/insulation box idea.
I figured the pipe running up the south wall should be painted black. Glazing or concentrating mirrors would again,more complex infrastructure.

Being as winter is here, I'll shelve this idea for now,though attic work is easier in the cold.