[archmagi]

For a sales or trading job, maybe a poker player can be considered.
But for any other type of job (decent job i mean), I would definitely kindly show the door to anyone like you described. My reason is: If I need experience, then it would be much better to hire someone who has had working experience and had some success in the position I'm looking to fill.
In comparison to recruiting someone who spent 2 years getting experience in poker (or any irrelevant job) I think it's better to recruit someone career minded straight off university.
One of the biggest down-sides I see with your suggestion is that someone who has turned pro straight off school has never had exposure to a corporate culture; never went to work at 9am every morning, never wore a suit to work (well, unless they play ni a suit which is unusual these days), etc etc. There's so much they need to get used to at work that it's not worth the risk.
I bet that should you employ someone like that, you will loose them within 6 months 75% of the time.