considering the capability of BD dockyards to built Durjoy class after learning from China for almost five year since the design commence in 2009 and starting to built the pair in 2014, one just need to wonder on how long BD need to learn and try to built a decent corvette (a note even till now still not hear news when BD dockyards will actually built type 56 corvette in house). And now talking big about built a full fledged AAW Frigattes with all of their complexity, Its beyond me actually.
Since you probably have little idea about Bangladesh yards (going by the doubts you cast above), allow me to entertain you on our capabilities. Bangladesh has the highest number of medium to large shipyards per mile of coastline in the subcontinent (higher than our neighbor in the West who arguably have the second most powerful Navy in Asia), and this most probably means much, much more than any large Asian country with a long coastline.
https://defence.pk/pdf/threads/dockyards-in-sub-continent-pakistan-standing.483091/
We have had a much longer history of building Western ships of all kinds since time immemorial. Indigenous Shipbuilding has been a century-old tradition in East Bengal. It is one of the earliest industries developed in Bengal based on its tradition of building boats and sea-going vessels. Many countries of Asia and Europe used to regularly buy ships built at Chittagong. Ibn Batuta came to Bengal in the 14th century and went back in a wooden ship built in a dock located at Sonargaon, Dhaka. Such historic ships are being preserved in European Museums.
According to the European traveler Caesar Frederick, Chittagong was the center of building ocean-going vessels during the middle of the 15th century. During the 17th century, a fleet of ships of the Sultan of Turkey was built at Chittagong. During the Mughal period, Bengal took the lead in the region in building ships and boats. The Mughal Naval Force had a large number of ships built at Chittagong. The British Navy used warships built at Chittagong in the famous Battle of Trafalgar in 1805. In 1818 the wooden hull frigate Deutschland was built in Chittagong and delivered to German Navy. During the first half of the 19th Century, the shipyards at Chittagong built ships up to 1000 DWT.
Even prior to that period, Buddhist monks used locally built ships in Samatata area (see diagram below) in the fifth century to travel to Myanmar, Thailand and entire Indochina to spread Buddhism. Samatata was the center of shipbuilding in ancient Gupta period (500 AD) because this was the Buddhist sea-lane lifeline from the Gupta empire which was the center of Buddhism toward newly minted Hindu/Buddhist countries and cultures in Indonesia and Indochina.
We have had more formally trained shipwrights, ship designers, universities with programs in marine science and engineering than any country of our size in South Asia over the years since WWI. The reason is that we need smaller river vessels and ships to travel locally. Often informal shipwrights will build passenger launches (ferries) carrying 1000 people in the middle of nowhere on a sandy island from blueprints.
Coming back to our recent naval builds such as Durjoy class (650 tons each) - those vessels were completed in
three/four months in a yard built in the 1950's.
This Navy yard (among about four or so large naval yards locally) is still considered a state-of-the-art facility for building vessels up to 10,000 tons and 3000 DWT coasters/bulkers of DNV/GL, BV and CCS classification are built routinely (I'd venture a guess on close to fifty or more ships every year) in over a hundred yards locally which are far below that standard.
To build this modified Jiangkai II class of 4000 tons, the four larger naval yards we have are easily capable of building at least two of them side by side at the same time. If you think this is 'talking big' - then you don't know our capability.
Bangladesh has experience building medium sized naval ships up to corvettes since the 1950's, but hasn't ventured into building frigates because,
- we mainly used to import (most recently from China and S. Korea).
- govt. purchases were rife with corruption
But that is about to change.
This is the Shipyard built in the early 1950's, where the modified Durjoy classes are being built starting with a view of BNS Nishan (These shipyards all have parallel modular build capability),
This is the Navy yard where the 4000 ton Jiankai II's will be built. I rest my case.
This is one of about a dozen
private shipyards that are all capable of building destroyers up to 9900 tons. Some of their recent builds shown below, starting with some builds for JSW India.
And the fact about what's 'beyond you', Bangladesh was supposed to be basket case forever in 1971, but in just a couple of decades, we had rebuilt our completely war-ravaged country from the ashes. And look at where our HDI level is today, in some areas they better than every country in South Asia and even Indonesia. This is fact.
Bangladesh can comfortably compete with other shipbuilding countries (India, Indonesia, Vietnam, Philippines) for building specialized smaller builds of ships for now - because our labor costs in that sector are half that of China.
Yes - half. And this is
without any incentive from our govt. I understand your labor cost in this sector is three times that of China - which means your labor cost is six times more than us. Maybe we can cooperate on Shipbuilding with your industry to take advantage of your higher expertise and our low labor costs, being that we are brotherly Muslim countries.
If Bangladesh decides to forge ahead with larger yards, there is very little in shipbuilding we cannot do. 
