We did experiment with offering ACH payments via a different service (Check Gateway) a couple years ago. We discontinued that, because the automated address and other verification checks required for online ACH authorizations blocked many legitimate payers, such that it cost more in declined payment fees and hassle for our lenders than it saved in transaction cost. Also, almost half of our lenders are outside the US.
We did request free payment processing for Zidisha, and have also asked Kiva to request the same deal for Zidisha. Two years ago we even had an online petition for PayPal to waive fees for Zidisha loans - https://www.change.org/en-AU/petitions/paypal-stop-charging-....
Thus far, our applications for free or heavily discounted payment processing have been turned down, and we continue to seek more cost-effective options.