Decks, Patios, Porches and Docks - Flooring Over a covered front porch

I just had a house built recently and I have a 31'x6' covered front porch/deck which is south facing. The porch structure is pretty substantial it is constructed on 6x6 posting sitting on concrete footers, 2x8 stringer carries the load and the deck frame itself is 2x6 and decking is 2x6 all pressure treated lumber. The decking has been replaced once by the builder and all new 2x6 PT lumber was pulled up and replaced because it keeps cupping and twisting and makes the front porch a bit difficult to walk on at times. I was wondering if I could lay roof felt down then screw on 1/4 to 1/2 PT plywood then dur-roc and put down tile or slate etc. Is that do able or will I make things worse. Any suggestions a welcome. Bottom line is I don't want to pull up the decking again. The porch carries the columns which hold up the front porch roof and I don't want to compromise the structure in any way.

Thanks

You can lay the #30 felt and then I would screw 3/4" CDX plywood to surface. Then you will have a flat even surface to start with. Using thinner plywood will have to much flex, especially for tile.
Thanks for listening.

Would it still be too flexible if I only used 1/2 PT plywood and then du-roc on top of that, each layer running in opposite directions? Any suggestions on tile types. I don't want anything too slippery.