Tiling over HotMop

Here's a challenge!!! I have a flat roof that has been coated in hot mop. I want to lay porcelain tiles over this and am trying to figure out how... My issue is that I only have ~3/4 inches from the top of the hot mop to the top on finished tile on the lower edge (allowing for drainage grading). This means that floating a layer of cement (normal practice?) would fail as it would be too thin (~1/2 inch).
I'm thinking about wet setting using a grout so that I get the strength, flex and strong bond to the hot mop - but will this really work?! Are there better ways of doing this?
Thanks in advance for your help!

DIY Guy:
"I have a flat roof that has been coated in hot mop."
Is this where they take an old flat roof whose membrane really should be replaced and spread a coat of hot tar all over the top of it to make it last a few more years? Is that what "hot mop" is? I like to think I know a little about flat roofs, but what you're calling "hot mop", I would call a "flood coat".

"Are there better ways of doing this?"
Yes. I think the best way would be to remove the entire roof and have a "sloped" roof put on. A sloped roof is where they insulate the roof with slabs of styrofoam insulation which has been cut by an electrically heated wire on a computer controlled machine. This wire shaves the top off that block of styrofoam insulation so that when the blocks are assembled in the correct order on the roof, they establish a gentle slope to the roof drain.

Over top of the insulation it's standard practice to put on two layers of fiberboard insulation with the joints staggered to protect the insulation from the hot tar, and then build up the roof membrane as usual.