i am already tell them, Bangladesh Navy should get the best bang for the buck, and in my opinions the second hand of U-209 ex Turkish Navy. Not this oldies with rotten looking metal scraps. We all knows the standard maintenance and use of NATO countries, they are very strict and they had a better log book and maintenance schedule in which you can use them and learn it before buying second hand equipment from NATO member countries. My self is very doubt if China had those kind of standard maintenance for their subs before economic boom era in 90' to 2000's.
And for the AIP's, i don't wanna to see my brave sailor using unreliable test bed platform.