Greetings,
Thanks for submitting this request.

The Convert To for Processing feature's primary function is to allow merchants to utilize a merchant or 3rd-party gateway which has limited or singular currency support. PayPal's latest integration methods allow clients to submit payment in a multitude of currencies (https://developer.paypal.com/docs/api/reference/currency-codes/). The PayPal platform should natively provide the needed flexibility to support client currencies, minimize conversions, and keep purchase flows as simple as possible.

Generally it is preferable, from a invoice and automated service provisioning perspective, to itemize and collection payment as a static amount. The Convert To for Processing feature introduces variable payment due to conversion and thus payment and service reconciliation is more complex. Additionally it may add another layer of complexity when reconciling WHMCS reporting and your accounting system. For these reasons we choose to leverage a gateway platform's currency capability when possible. The PayPal Payments integration is one such case.

My suggested route forward would be to feedback to PayPal Merchant Technical Support - or your PayPal account manager - that they add support for your desired currency to the PayPal REST Payments API. The module in WHMCS is able to utilise any currency supported by PayPal, so as soon as it's added, then you will be able to process transactions using it.

In the meantime, there are no immediate plans to discontinue the PayPal Basic module, so you are welcome to continue using it until such time that PayPal expands their new platform to your desired currency.