Regarding to the topic,
If bitcoin build a headquarter bank, then the identity of bitcoin will not be the same as it is right now.
It will surely be implemented of having tax of bitcoin into its respective place where the HQ is built.
We all know that nobody owns bitcoin, (correct me if I'm wrong).
Maybe it is possible that there will be a bank supported by bitcoin payments.
Well as for as my opinion is concern so I think if bitcoin make headquarter bank so I think bitcoin can be increase with high price investors, traders and other people can be very high as well and it will be more easy for all investors to keep their bitcoins with them which will be more secure and I think that bank can also provide them some extra services like credit or debit cards.