There are certain advantages of operating ''costly crap from the west''. I make no pretense at being an expert on Made in China defence products. Whether it's camo uniforms, small arms, lorries, jets, submarines, etc, Chinese companies can meet all the needs of any military, but there are still certain items [if the decision was mine] I would rather source from the West. Similiarly, if the cash was available I'm sure Bangladeshi decision makers and defence planners would like to acquire certain items made in the E.U. or the U.S.
It's a matter of threat perceptions and economics. Not only are submarines expensive to buy they are also expensive to operate. A shore support and training intrastructure will also have to be established.
If a Bangladeshi naval ship with special forces embarked was in the area I don't see why it would not be able to do the same. No offence but South Korea has a biggger economy and is better able to fund out of area deployments. Due to having a larger navy it can deploy assets in the Gulf of Aden without reducing it's ability to meet it's comittments at home.
There has been a lot of talk about what Bangladesh operates and what it should buy, etc, nothing wrong with that. For the benefit of those who are not very familiar with Bangladesh, perhaps the Bangladeshi's here could provide more insight into the threat perceptions of Bangladesh, it's disputes with it's neighbours, etc,?