There are two major problems with this module.
1. From the admin area, you cannot update the card number via the usual UI. The card number ends up being stored in the WHMCS DB (a PCI security issue). This needs to be enhanced so that a token is created and stored.
2. The customer cannot update their card unless there is an UNPAID invoice in the system. This needs to be enhanced so the customer can update their card details at any time. (and they are stored in a token at eway).
3. There is no way to migrate customers from the OLD eway module (where the card numbers are stored locally in the WHMCS DB) to the eway token method. There needs to be an easy way to migrate a customers card number FROM whmcs to eway.