WARNING: Just my opinion and speculation.
Like the navy officer and other PDF members said it will take time to buy LHD and we will need to get other ships like air defense frigates, subs and large logistic support ship/auxiliary vessels to support. Also the procurement of LHD heavily depends on BD's economy and development. So like others said, there's a strong possibility that it will not happen before 2030 as it seems to be part of long term plan. Lots of things still didn't materialize so even 2030 is just a wild guess.
Why do we need a LHD? IMO for two reasons mainly. First reason is to counter both of our potential adversaries aircraft carriers with a small but potent aircraft carrier suited for our economy, navy and sea territory. As we are moving forward to acquire larger air defense frigates, submarines and logistic ships, the possibility for BN to become a blue water navy with limited range power projection beyond EEZ is also increasing.
The navy officer said the aircraft carrier will not be small or large. So i guess my hope for something like 8000 tons Algerian LPD Kalaat Béni Abbès or the Qatari navy variant is gone. If i think about a medium LHD then only four examples come to my mind. First three is Dokdo, Mistral and Juan Carlos I class (including the Turkish and Australian variant). I didn't include Chinese Type 075 and Type 071 cause i considered Type 075 as large LHD and you can get better LHD at the same size of Type 071.
The fourth and last examples can be the most ideal choice for BN. The new Italian LHD Trieste. I love how Italy arms it's carrier and i would love to see BN follow Italy's example. Besides we can also take Izumo class as example.
What i was trying to say is the LHD should be able to be configured as both helicopter carrier and light aircraft carrier. BN should keep provision in it's LHD for integration of STOVL fighter jet so that we can get one in future if we can't get it now. Depends on our economy and USA.
Now there's only two options available i think. First one is Spanish AV-8B Harrier II. Though Spain will operate the fighter till 2025, it plans to replace it with F-35B. Now we know that American aircraft can operate longer than their original service life, so if we manage to buy those AV-8B and fly them from our LHD for at least 20-25 years then it will be a great low-cost solution.
Second option is......yes, you know, the F-35B. Now, thanks to China the US is suddenly getting too friendly with BD. If we can manage to use that as a chance then we can get that fighter jet for our LHD. A squadron consisting of 12 AV-8B or F-35B can be a great addition to our future LHD.
Besides a STOVL fighter jet, BN can fit it's LHD with bow mounted sonar, acoustic jammer, anti-sub decoy like the Izumo class and 76 mm naval gun and at least 8 cells VLS with SAM like the Italian LHD Trieste or Algerian LPD Kalaat Béni Abbès. Sec Ceptor can be ideal option if we choose VLS.
Now with those four particular specifications (12 fighter jet, ASW capability, 76 mm gun and 8 cells VLS for SAM) including other general characteristics, BN's LHD will become a quite formidable light aircraft carrier with both defensive and offensive capability. I believe it will be able to patrol alone or with smaller escort with those capabilities even in wartime. These will also help during a amphibious assault.
So this is what i meant when i talked about countering our potential adversaries aircraft carriers with a small but potent aircraft carrier in my second paragraph. It may not be equal to IN's aircraft carrier but it will still pack quiet a punch. That's why the LHD should be built mainly focused on IN. So that the LHD can be a huge force multiplier which can create strong deterrence against any naval blockade or threats and can cover larger area quicker than frigate. Besides the LHD will be able to supplement future Barisal airbase from where a maritime strike MRCA squadron is expected to be operated.
Second reason is Humanitarian Aid and Disaster Response. Our country often gets hit by cyclone, the southern part takes the most damage. LHD with a hospital facility can be a great help for HADR. During cyclone Sidr two USN LHDs assisted BD, we can take that as example.
To keep regular presence in BoB, BN may need at least two LHDs i think. Anyway i don't think we really have to buy LHD for attacking other country though our armed forces exercised beach landing probably last year. Also i believe we don't need to buy helicopter separately for LHD. We can use our Mi-17 for that. We can also use our BTR-80, future amphibious tank for amphibious assault. If BTR-80 does't satisfy our requirement then we can get FNSS ZAHA AAAV from Turkey. We can build the LCUs for the LHD in our local shipyards. To be honest i think it's possible to build the whole LHD in our future yards at Borguna (KSY) and CDDL to reduce the cost.
I know i asked a lot and it depends on lot of things but we are talking about a helicopter carrier which will cost a lot anyway with all the necessary things. So if GoB wills to spend a bit more BN can get a potent light aircraft carrier in disguise of a LHD. Again it's just my opinion.
P.S:- For those who still couldn't find the source about LHD, it's 6th Defence Port Turkey's 2nd Webinar.