You are talking nonsense. If foreign airlines are inefficient then local airlines would be thriving. But this is not the case.
Why are local airlines doing so poorly compared to foreign airlines? You need to ask the passengers who chose foreign airlines over local airlines. All you are doing is to deny people a choice.
And if you drive out foreign airlines, don't be surprised if Bangladesh airlines are banned from flying to certain countries, because there will be retaliation.
The Middle Eastern countries will especially retaliate, including going as far as deporting Bangladeshi workers and reducing quotas for work visas.
You think Bangladesh has some kind of leverage in this matter, but it doesn't. No one will win. All will lose.
Are you really comparing the Bank of Bangladesh to the Bank of England?
The pound is a reserve currency. I don't need the Bank of England to convert my pounds to dollars. I can just do that in the FOREX department.
Not so with the Taka. This is why foreign companies demand repatriation of dollars in order to do business in Bangladesh. I guess you want Bangladesh to not only destroy FDI but also Bangladesh's own exports. Trade is reciprocal after all.