I think countries will not go into Unions, unless they are ready. So community of nations is the first step, just like it has happened with EU. Some parts of many countries want separation, but they will be part of other bigger Unions of countries, just like former Yugoslavia has broken to many parts, but they are all becoming part of EU. Places like Xinjiang, Tibet, Kashmir and North East India, I believe are pretty much lost causes for complete separation, for the foreseeable future. All we can hope for is maintain, regain and increase further autonomy of these regions and ensure the rights for indigenous minority living there, putting world pressure on the concerned large states.
In a future that will be dominated by large states, no small country, I believe, will afford to remain isolated and without its own team, even at the expense of loosing some level of sovereignty. When countries in a community are developed to a certain extent, they may not need to migrate to other places because of economic reasons, so without migration, there is no threat to culture and social harmony.
Bangladesh is in SAARC group, but this group has no future, other than economic relationship. As you may know, Bangladesh was the Eastern part of Pakistan before 1971 and became separate in 1971. The original reason why Bangladesh land mass became a separate country from India in 1947 still exist. There is a trust deficit between majority Hindu India and majority Muslim Bangladesh. From knowing India well, we understand that India's Hindu nationalists are a threat for Islam and Muslim people anywhere in the world, including Bangladesh. It is because, some in India have not been able to come to terms with the fact that Islam has spread in the subcontinent and has brought great demographic change in the region. Many Indian websites openly call for attacking former parts of British India, such as Pakistan and Bangladesh and convert the population in these regions back to Hindu. Indian Muslims live under discrimination and in most big cities Hindu's do not even accept them as tenants or buyers of property in most of part of the town or city. So Muslims are forced to live in Ghettoized small restricted areas. But these are just the tip of the iceberg. There is a particular type of Hindu nationalist that consider Islam and Muslims as existential threats. Like Neocons who spread the canard that Muslims want to engage in Jihad and take over the whole world in a conquest and make it Muslim, and thus establish a world wide Khilafat, this brand of Hindu nationalists believe in this same wild theory with a passion, and use it to dehumanize Muslims, and to justify any acts of current and future aggression against Muslims, including total annihilation or at least brutal subjugation and genocide. After the 9/11 incident, this same tactic was used in the US to start the GWOT and the result continues today. They currently use this same theory to justify putting dams on all of the common international rivers that run from India to Bangladesh and end in Bay of Bengal and divert water as and when needed. Farakka Barrage has caused desertification and increased salinity in large parts of Bangladesh. Bangladesh politics is also controlled by India using its agent political party called Awami League. Also, they spread baseless rumors that Bangladeshi Muslims have migrated in large numbers, in order for them to create a case to take away citizenship of Bengali Muslims of India in the future. For the long term, Indian Hindu nationalists want their "civlization space" back from Muslims and also eliminate Islam from the face of the earth, so it no longer remains a threat for them. On this issue they find willing fellow traveler with Zionist Islamophobes, which is the main basis of close relationship between these two states, India and Israel, although on Iran issue, this relationship has frayed of late.
The solution for Bangladesh is to reach out towards ASEAN, build roads and railways through Myanmar and make ASEAN a success and if Korea and Japan can get more involved in ASEAN, that will be another boost for all parties and nations involved. There is a section of people in Bangladesh, who think that it is possible to be in the Chinese camp and counter this multi-level threat from the large neighbor state of India (who we have border with on all 3 sides if you look at our map) which is not just another neutral neighbor for us. I am not one of these people. I believe in more increased economic relations with both India (even giving them transit, if they agree to deal with us fairly on water management and other issues) as well as China, once land routes via Myanmar is a reality. But for the foreseeable future, I personally cannot see Bangladesh in any kind of Union or community of nations with India. I think most Bangladeshi's would rather become a part of expanded ASEAN for mutual security and development to protect against the threats from neighboring large states, which in our case is India, but for most ASEAN states as well as Japan and Korea, happens to be China.
