Normally, a cement deck or patio is sloped to support drainage of water that would otherwise accumulate on the surface and cause some problems. These surfaces do not look so good with tile on them or any other finish for that matter. This is because of the slope and how it makes pieces of flooring run together in certain places.
A much better look is established with a totally flat surface to set tiles and other flooring on top. Since you cannot have this with concrete porches or decks, what are you supposed to do? You do need to keep the base concrete with the drainage slope. That has to stay for good reason. Generally, you don’t want to go ripping parts of a house down unless you need to.
Just because you want a nice, flat tile set patio does not mean you have to start from scratch. Just use the one you already have. Make it simple and use adjustable deck supports. These supports allow for a totally level and flat grating to be lifted up above the slab no matter what the different depths are. The actual height of the deck base is adjusted so the grated surface will be flat and level.
Many deck systems do not really allow for tile installation and the classic slab porch does not look very good with tile as is. You can still have a system installed that will allow for good tile setting. This will be the adjustable deck that is mentioned. It is not a metal deck, so it is made with a special reinforced fiberglass structure.
Water from rain and other sources will still drain off the deck or porch through the tile joints. Meanwhile, a good level is maintained so you will have a beautiful deck.