An ageing gigolo con man who plays a naive socialite to finance his last chance at the big shot has been done to death. Spoiler Alert: It never ends well for him.

One of my favourite movie about a chancer who uses his roguish charm to climb the social ladder, before falling in love with his target and ending up rejected is?Barry Lyndon. That movie was superb for his time. The soundtrack is really the thing that transform that movie into a great melancholic tragedy.

Anyway, personally I would flip the script. Make the naive socialite the main character. She is new and introduced to a world of shark. Will she sink or swim? Her “loss of innocence” journey seems to have more mileage. A good movie on that very theme is?House of Games,?a well known David Mamet movie.
It flips the script in the sense that the initially naive psychologist finally reveals herself to be a thrill seeking sociopath.

I agree that It is unimportant to know why the dancer lost the competition from the Logline. My objective was just to explain why she would hire a skilled MMA fighter. A dancer is about grace and fluidity, clearly not something you associate with a street brawler.
Your hook is that she is hiring somebody unexpected to win that challenge. However in the concept of the Logline, that hook has to lead to a “why not, I dig that” reaction rather than a “wtf, that does not make sense” reaction. ?You don’t want your Logline becoming a meme. why not hire a plumber or a skydiver?

You need something in your Logline to tell that hiring that skilled street fighter makes sense.