Ponga has said he doesn't want to play in the halves, so this is a moot point.
But even if it wasn't, the idea of Best at fullback makes no sense. He's got no real experience playing there, there's nothing to suggest his communication in defence would work, there's nothing to suggest his positional play would work. On top of all of that, he's never displayed any real ability as a ball player - this is still the guy that couldn't execute a very simple catch and pass against the Panthers in 2020 - you want him making decisions as a ball player on sweep plays?
Best is a physical talent, and a good runner of the ball. But his future skews much more towards second row than it does fullback.