We recently had a client who uses WooCommerce and conducts business globally. They use PayPal and BrainTree as their payment processors.
The challenge they faced was that they needed to process payments in USD, AUD, and EUR.
These orders needed to be according to the region in which their customers were coming from.
We solved this problem by using Currency Switcher plugin.
However, this only gave the options of having multiple currencies in the shopping cart (WooCommerce), but when going to anything other than PayPal Standard, it would default to the default currency with that payment module.
To address this, we rewrote the function in the BrainTree module to check the currency (set by Currency Switcher and WooCommerce), and then automatically assign the correct merchant account ID in BrainTree.
Now, payments are routed to the proper Merchant Account ID with BrainTree, based on the currency.
If you are facing a similar problem, let us know. We can help.