There is the Check 21 Act[1] which does not need ACH and is not subject to any of NACHA rules, regulations or fees. Banks already use it and if it is integrated well, it brings down the payment time to 24hr.

Check 21 describes a file format that is used by banks and service providers to upload payment information to FRB.

[1] https://en.wikipedia.org/wiki/Check_21_Act