Interesting idea. Do you have sand now. Frequently people use sand and plants and get great growth with proper light and lighting routine and some fertilizing.
Turtles are usually not too careful and you would need to select plants which are flexible and not brittle and can grow quickly to recover being battered and run over.
What is your tank size now, light? Do you know the K rating if it is a bulb, it should be on an end like i.e. 6500K, 7200K.
What kind of turtles, how many and what filter are you running?
Are you familiar with the nitrogen cycle? If not check out the article in my signature for useful, and invaluable info.