You can do the standard wire transfer offered by the bank and transfer funds from your checking to the customers checking etc. I am not exactly sure why you have to involve Paypal.
Also for most people who actively work with Paypal, having the funds within the Paypal account is just as good as having funds in the bank account or even better. Paypal is just like a bank.
If your customer has the Paypal Debit Card, he/she can withdraw up to $400 at any ATM daily and deposit into their bank account right away.
I can also imagine Wells Fargo offering their larger authorize.net merchants an option to receive funds immediately upon successful cc processing, basically a line of credit.
Hope this helps.