You know, those nukes are NOT in the control of host countries but in control of USA. Only exception is UK. If Pakistan were to deploy its nukes in Bangladesh under similar terms the problem will be back again. What will ensure that Pakistan will actually retaliate to a conventional attack on Bangladesh with nukes, even if those were stationed in Bangladesh?
Will Pakistan risk itself to be destroyed to protect Bangladesh?
Those nukes are designed to be fit onto the Host Country's aircraft and deployed by their pilots if the need comes, of course you can't on your own decide to use them. But its not a simple matter of the US have aircraft and nukes deployed. Thats the case with every major foreign base deployment, its a little more involved than that. for example, Japan and South Korea are not nuclear weapons sharing states, but you can bet US nukes are certainly deployed in those countries.
Nuclear Weapons Sharing is exactly what that term implies, sharing/joint control. The whole point of setting it up as that in the first place was to dissuade the states part of the program from pursuing their own nuclear programs.
As to the last question, umm... yeah, that the whole point of a mutual defense contract and nuclear umbrella. Its to exact a price, that if Bangladesh gets invaded, we all die together in a MAD scenario(in this case, Bangladesh, Indian and Pakistan), the point is to increase the threshhold to where it actually functions as a deterrent.
Idk if a conventional strike would be answered with a nuclear, the scenario would likely need more of an impact.
Essentially what is being proposed here is more akin to the relationship before 1970s, its not going to be East Pakistan, and its not going to be based out of Islamabad, where power is hold by one side over another, Both States will be sovereign, but there would be a mutual defense pact.