Bengalis are smart. They can leverage their relations with big powers to stay out of a direct conflict. India, China, USA & to a lesser extent Pakistan, can all counter balance each other & Bangladesh can carry on as it does.
Bangladesh is a small country with a big population. It has no ambitions within the region & beyond. Its rightfully concerned about economics more than anything else.
Embarking on armament is going to create more threats for Bangladesh than bring security. A squadron of J10s or Typhoons is only going to invite a couple or more squadrons from India & Myanmar on its borders. Bangladesh can not afford to be seen as a threat to India & does not want to antagonise India.