Maybe a lot of people have design expertise about cryptocurrency but this is unique because you accept payment with bitcoin, I really support your idea and design
This business can be promoted on the global market with a good and unique design so it will attract many traders to collect these t-shirts
The design he made is very interesting but to add it is best to come up with more design yet more appealing to the client. Anyway, he has a good idea by promoting bitcoin to their country which he will accept bitcoin payment. This is good to start a business on your own with more marketing ideas so people will buy your product.