First you have to explain in detail the meaning of BTC being legally accepted, accepted as an investment vehicle or as a means of payment? If it is accepted as an investment vehicle or digital asset, maybe this makes sense and in the future there will be regulations governing this issue. but if it is accepted as a means of payment, this seems impossible because it is impossible for there to be any other legal means of payment other than fiat currency.
I think the problem will even be from the laws and legal force in each country,since the laws are very different in the countries and finding a solution that will suit absolutely everyone will be unrealistic.I think for any user the most important thing is an exchange in two directions, and the laws and loyalty of the state are not so important.