Prepay for items using a balance system???

[midwestwebsites]

The Problem:
I'm working on a project that uses OSCMAX 2.0 RC2 for a site that features file downloads; however, due to the pricing structure of those downloads I'm getting killed on the merchant account transaction fees. Currently we are using Authorize.net to collect our payments. I thought about batching transactions as a few of our customers purchase multiple times within a 2 day period; however this has 3 problems A. I don't know how to batch transactions with OSCMAX and B. batching credit card transactions adds a lot of problems due to mastercard / visa rules for data security, C. Not enough customers purchase multiple times to help my bottom line enough.

What I'd like to accomplish:
I'd really like to find a system that requires customers to prepay for a set balance (such as $5.00 or $10.00) and then purchase the items from that balance -- similar to the gift voucher module included with OSCMAX.

The Problem with Gift Vouchers:
The reason I can't use the gift voucher module is 2 fold:
A. I don't know how to limit customers to being able to purchase only gift vouchers with their credit cards and allowing them to buy the $0.99 products **only** with their gift voucher balance. I don't want customers to be able to purchase the tracks via their credit card - I want them to use the Gift Voucher.
B. Gift Vouchers need to be manually released from a queue. I need something that is automatic as soon as they purchase the gift voucher.


Does anyone have any thoughts on the subject? I'll be very grateful for any assistance you could provide.

Thanks in advance,

Jonathan