I think Bangladesh need to concentrate on its economy until 2030 and dont need to buy new fighter jet along the period.
Bangladesh then can start replacing all of their fighter with 5 generation fighter starting in 2030 when its economy have been tripled.
KFX/IFX program can be one of the option if this program is successful and can reach its mass production phase in 2026.
BAF cannot wait any longer and it is shameful that a country like Myanmar that has a GDP five times less has a much better air-force.
As BD has been wasting so much time already and still in 2020 has not ordered any modern 4+ generation fighters, it does not make much sense to waste too much treasure on buying say 100 4+ gen fighters over this decade, as they will start becoming obsolete in the 2030s.
The KFX/IFX program will not really be suitable as too much of the tech will be US/Korean. Korea is heavily under US influence and could easily buckle to US pressure.
I would say get a couple of squadrons of 4+ gen fighters from the West now, then wait till 2025 when the FC-31 should be ready for export and start ordering this in numbers as the financial capability of BD allows.
Myanmar is not that much of a threat as it is so tiny and so could be taken care of with maybe 2-3 squadrons of 4+ gen fighters at most and then BAF could be geared with much larger numbers of Chinese 5th gen fighters to be able to deter the Indians for the longer term, who are the real threat to BD.