is a good idea IMO
No, you should not see a spike in parameters from dry sand....
Yes, CC is okay under fine aragonite. What you MUST do is use a fiberglass screen. Get it from Home Depot. You add the CC, put the screen over it to separate the two layers. Have it come up a little on the sides, like a tray.
CC traps detritus and there will be some critters that dig in the sand and they can get that detritius down there. The screen keeps the layers separated and prevents detritus build up.
I agree that 1x1 is too small to make a major impact, but it will help. Add in some cheato and a hang on light and you've got a nice fuge setup. Avoid any fish or inverts that dig or eat algae. It's a great place for bristleworms