Very interesting idea, I would like to try it as an amatuer. If you can adjust the bounce and the speed seperatly, it would be really good. Imagine if amatuer players can adjust it to be slow like clay, but bounce low like grass or carpet. I think it can be really cheap in long term and the biggest problem with tennis for me is the weather. This could minimalize it, because it would still be healthy not like HC, but no problems with rain.