I disagree totally.
It is impossible to cover every inch of potential landing ground, and even after detection, to mass defensive troops at the spot will be impossible.
1. At first this argument would depend on heliborne assault penetrating through Manpad/short range AD screens. Which btw, are not expensive at all, and can be procured in numbers to cover all areas. (A Manpad has an effective range of 5/6km) Very much easily hidden and dispersed and unlike MRSAM or LRSAM does not have a large static physical and electronic signature when operational.
BD army has variety of manpads in service today, they understood its significance enough to initiate a project for local production through ToT. So, I think we got that cover, maybe not today right now but in the near future.
Bottom line is, I do not believe in today's operational envoy heliborne assault force can penetrate through distributed manpad screen and survive enough in sufficient size and numbers to achieve any meaningful tactical gain. Ukraine war is a good example to examine failure and successes of attempted heliborne assaults in less adverse conditions.
The concept of universally available sensors is again a theoretical one, and has to be demonstrated as possible. These will not be acquired. Instead light tanks will be purchased, and self-propelled artillery, and all the bells and whistles.
2. Yes, our discussed sensor density is theoretical as of now. But given we are also making prediction on how limited budgets likely to be utilized, I would like to present indicators on why what you are saying is may not be the case.
First, let's discussed how
localized sensor density across the breadth of battlefield is achieved. What we can tell from Ukraine lessons, 85% of its are very cheap and small UAVs (majority of which are commercial or at least assembled from off the shelf kits) while 15% are land based EW systems. (Passively listening into the EW spectrum m and often directing tactical UAVs where to look) The term 'transparent battlefield' maybe little bit misleading because it doesn't include the all of it. In fact, the further and further you go into enemy's depths (operational and strategic depths as coined by US Army) it is increasingly less and less transparent (unless you have air superiority. Which BD would never have). 'Transparent battlefield' is a more accurate description for the line of contact and adversary's tactical depth. This is what I meant by
localized sensor density. That if achieved denies any tactical surprises whatsoever.
BD army has ran behind fairly expensive large drones for a while which could be aquired only in limited numbers. Just like you say. Finally they settled for TB-2. Which maybe cost effective for its class, still costs in millions and can never be procured in large numbers realistically. However, lately army is increasingly focusing on smaller and smaller UAVs and their potentials. It can be seen in its procurement patterns. (I can post tender documents, articles from army journal but that would unnecessarily lengthen this. So I hope you would take my word for it.) Like Bramore C4eye, RQ-21A (Already procured) And several other ongoing procurements. (In small numbers, nevertheless it points toward right direction)
But more importantly local development, which again like Manpads production initiative underscore its significance in the minds of BD military planners.
These are very primary local examples and armed forces were experimenting with them. However, after successfully developing the BBT-2 trainer, they have officially sanctioned an ongoing turn-key project to develop a full fledge tactical UAV.
Auspicious move. Undertaking R&D project on UAV was a long cherished dream for BAF. After 10 years of work it has come to a shape. The said UAV is now equipped with sophisticated and complex electronics like GPS guided autopilot, live video transmission equipment, ground control station and various other features.
-From army journal
And then of course recently we have this news-
"Sky Bees Limited to Establish Drone Manufacturing Industry in BEPZA EZ
Bangladeshi company Sky Bees Limited is set to invest US$ 45.95 million to establish an Unmanned Aerial Vehicle (UAV, commonly known as drone) manufacturing factory in the BEPZA Economic Zone (BEPZA EZ)."
The signed an agreement for this. It's initially for commerical purposes. But these systems can easily be adopted for military use. (Just like in Ukraine)
www.bepza.gov.bd
As for land based EW systems, (the unseen aspect of the localized sensor dominance across the breadth of battlefield) army has procured these from Thales and looking to get more of various types from Türkiye.

TRC-274
Third, why cannot a bridgehead be established by light infantry and special forces? They will not be expected to do more than defend a perimeter.
Fourth, it is mind-boggling to think of every inch of every river bank being within striking range of armour, mechanised formations and artillery dug in into pre-determined positions.
Of course, every inch of river bank cannot be covered with armor and mechanized forces. Nor it needs to be.
1. First of all, even after theoretically stablishing a foothold/bridgehead, I can most of the time reposition my armor and mechanized units (to engage your light infantry and SOF, or gain the position of advantage) faster than you could bring your own sufficient heavy firepower to this side of the river.
2. secondly, just because every inch of the bank is not covered, doesn't mean you could land anywhere. Simply for the fact that after bringing your formations in the bridgehead, you have to follow through with subsequent maneuver into my territory to make tactical gains. And obviously all of the river bank are not good positions to start with. In fact some places would be bad choice and may put you in serious disadvantage after supposed successful landing. That already narrows down potential bridgehead sites.
However, most importantly, good old artillery when dispersed can actually pretty much cover all necessary spots on the river bank. And when coupled with localized sensor dominance it can enable a devastating reconnaissance-strike complex, break up enemy formations and attrit them down.
(See the new buzzword is 'maneuver fires instead of maneuvering forces' or 'concentrate fires instead of concentrating forces' to achieve the effects. I.e. due to absolute superiority of fires over 'protection' today, concentrating sufficient forces to tactically punch through is often porvibitively expensive. So you will try to mass effects from dispersed position instead of physically massing forces.
In fact this is exactly what happened at
battle of the Siverskyi Donets in may 2022.
The Russians Lost An Entire Battalion Trying To Cross A River In Eastern Ukraine
The better part of two or more Russian army battalions—potentially 100 vehicles and more than a thousand troops—in recent days tried to cross a pontoon bridge spanning the Siverskyi Donets River, running west to east between the separatist provinces of Donetsk and Luhansk in eastern Ukraine.
Ukrainian artillery caught them at the river bank—and destroyed them.
(See the images below)
The Ukrainian army’s 17th Tank Brigade spotted the bridge, using one of the many small drones that function as the army’s eyes over the battlefield.
But it was the brigade’s artillery battalion with its 2S1 122-millimeter howitzers that apparently got first crack at the Russian bridge and the vehicles and troops concentrated on and around it, out in the open.
The better part of a Russian army battalion—50 or so vehicles and up to a thousand troops—in recent days tried to cross a pontoon bridge spanning the Siverskyi Donets River, running west to east between the separatist provinces of Donetsk and Luhansk in eastern Ukraine.
www.forbes.com
See, it wouldn't have mattered if the Russians somehow stablished a foothold, Ukrainian artillery coupled with their ISR UAVs would have done the
exact same thing. And that was largely achieved without engaging the Russians in direct combat with their own infantry and mechanized formations.
The bottom line is that Bangladesh will not be able to juggle a military budget that will allow the military, land, sea and air, to fight a conventional war.
Disagreed.
@LeonBlack08 @AbuShalehRumi i added some meterials on indigenous UAV developments. It may interest you.