Following the existing standard would make sense if Bitcoin was of the same type the standard was created to cover. Putting cryptocurrencies under/within the existing standard for fiat currency symbols implies that it is of the same type. But cryptocurrencies are a whole new technology, a vastly different invention, the purpose of which is to replace the old type of currency that requires trust, middlemen, authorization/permission, transfer limits, transfer fees, ridiculous delays, participation in a debt-generating usurious fractional-reserve scam, etc.

And what do you mean by disrespecting Bhutan? The Bhutanese ngultrum is represented as BTN (like the TV channel from V for Vendetta), not BTC. Appropriating the Thai bhat symbol, BTC, is perhaps a bit disrespectful though.