Your tank looks awesome as is.
I have a setup with a 20 gallon tank for one of my geckos and have had sand for the entire life of the gecko. I've had no problems with the use of sand and use dishes to feed mealworms. I seen no change in health of my gecko and he is a health 115 grams. So if you wan to make the change there will be no problem.
I agree. Why would you want to change it? It's a pretty sweet setup. I would say that if you even have to question somethings safety it would be best not to go with it.