I'll be customer #1 on the day you first release this.... if.....
You add at least 1 alternative to paypal inside the add-on. Not after release, but with the release (always hear how X developer says they'll add it later, but never do).
Amazon - - - - - - - - - - - -
payments.amazon.com
Google - - - - - - - - - - - -
checkout.google.com/sell/
2CheckOut - - - - - - - - - - - -
www.2checkout.com
Payza - - - - - - - - - - - -
https://secure.payza.com/?xitBnNpPwhUSZr+0FelbPw==
Stripe - - - - - - - - - - - -
Stripe.com
Amazon maybe the easiest to code for, it's basically paypal re-branded.
But any alternative would be a blessing for us who can not use paypal. It doesn't have to be one of the above listed... Just a few examples that there are alternatives.