Try this for an crude idea.
Make the top surface of the rotating platform have many vertices scattered over its surface (grid pattern?).
When the play stops walking (not sure how you will test for that?), find a vertex on the platform
that he is roughly above, then with every move of the platform, re-align the players x&y co-ords with
the new x&y co-ords of the vertex he was standing on.
Better - c_move him(absolute) by the x&y CHANGE the platform vertex had this frame.

Ive got another idea in mind, but I'll need to think on it a bit more first.