Does This Sound Like A Good Storyline For A Book?

It’s set in the future. The whole of England has been turned into what is basically a giant prison where criminals are sent for really bad crimes (e.g murder). These criminals have the option after being found guilty of either being sent to live in this place (known for being really awful), or being put into this ‘contest’. The contest is where fifteen prisoners at a time are put on a small island, and if they are the ‘last one standing’ then they are allowed to go free. They are allowed to take out their competition on the island (kill them, backstab, whatever).
The lead character was framed by someone, and found guilty at his trial, and chooses to take part in the contest rather than live a life sentence in the jail. The main part of storyline is about his fight for survival in the contest.
On the contest island, there are fifteen prisoners at a time. There are also lethal animals on the contest island. Minor part of the story but I thought I’d mention it anyway.
Anyway, what do you think? Could this be a good novel if written well?