Hello!
I'm WHMCS admin user/developer already since v2.2 (somewhere in year 2006), did many template customizations, hacks & hooks, provisioning modules and payment gateways (last was The Bitcoin & Ethereum payment gateway for WHMCS 7.7.x).
I would love to blend TAP code for your payment WHMCS gateway.
Looking forward to work with you,
Mathew