Sadly, for what you want to do, you essentially need to be a merchant bank yourself. Your business model seems to involve collecting payments on behalf of other people. Most merchant agreements from ANY bank or service provider would prohibit this activity.

Without the correct processes and procedures in place you open yourself up to issues involving money laundering and tax fraud. To do this right you need to spend the money on the identity, security and conflict resolution processes and procedures to ensure you mitigate this risk. The costs of real merchant services will pale in comparison to what you will spend on these issues.