Just about any payment method other then handing cash to someone has a reversal risk.
So, even if they fund with a debit card 6 weeks later the funds can be pulled back. So, now you have to acquire the BTC and sit on it until you are sure the funds clear.
How are you going to handle the KYC? There are a ton of places that will do it for you for a fee. But now they have access to your site / API calls so you are at risk that way.

And so on.

-Dave