The market for the crypto gateway is too small currently to think about a B2B model. I'm pretty sure none exist nowadays and there is surely a reason. There is no demand for it, so no use to supply a solution. You will spend resources for next to nothing or you won't get a return for several years. Ending with a big disappointment.

Since it is a business and it's supposed to make money (the much as possible) it's wise to follow the B2C road instead.
If your business activity becomes more important later on, you could always switch to B2B. But within the next 5 years, I don't see any niche with the B2B