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 Ethereum payment gateway for WHMCS 7.7.x).
I would love to brain-storm, configure and help you tweak anything on WHMCS as well as upgrade your braintree payment plugin.
Lets chat and discuss the details, I will then be able to give you time & cost estimate.
Looking forward to work with you,
Mathew