Let's take the BOF lineup piece by piece and you will see that there's little to no redundancy
Not that all the BOF will be on only 1 wheelbase based on the SA-L architecture but for BOF
1- Hilux / Innova / Fortuner
Pickup / Minivan / SUV
Midsize Off-road sport Capabilities
2- Tacoma / 4 Runner / Prado / GX
Pickup / SUV
Midsize Off-road luxurious Capabilities
* The only redundant here is the Prado with the GX , there's even a Prado trim named Prado GX "not the most lux. Prado thought"
= The solution is to turn the GX in Lexus Lineup to a sport rear wheel drive CUV , which will give the Prado more space for the upper lux. trim
3- FJ70
Pickup / SUV
Its very important and essential and it's to Toyota BOF lineup as G to Benz lineup, it's sturdy, rugged and have a lot of heritage by it's own
4- LC200 / LX
This is the second redundancy point where they are technically the same and honestly the Land cruiser naming decreases in order to give the LX the space so it will be more logic to turn the LX also to ultra lux. rwd CUV aka Bentley/Range Rover competitor and leave the Land cruiser naming to shine and grew again maybe returning the Cygnus naming and make the Land Cruiser naming as a new brand just for BOF vehicles
5- Tundra / Seqouia
Pickup / SUV
Last but not least the American couple that Toyota shouldn't leave them ever as long as there respective categories still exists
These distinctions are very clear, yet I am not certain it is this "choice" that makes Toyota/Lexus BOF SUVs sell, but rather the general Toyota/Lexus proven image of durability/reliability. When you look at the models, there is no regional redundancy, because those 'redundant' products are simply not available (with the exception of Land Cruiser/LX everywhere except Western Europe, where they are no more for sale and one never was as far as I know). In Australia you can't get anything the NA gets, in NA you don't get those models produced in Thailand (Hilux, Fortuner, Innova) and those for the Australian market etc. In Western Europe there is nothing else except the Hilux and Prado, Lexus has only CUVs. When you look at Toyota's competitors, they are mostly the same world wide, with for example the Ford Ranger now coming to NA. The Ford Ranger competes against two Toyota's, the Hilux in some markets and the Tacoma in other markets. Both these cars could be the same ones, even if produced in different regions, and also have different names, something that is not unusual at Toyota. There is no issue with the models 3-5 that you listed, but more with 1-2, where one truck and one SUV, with its van version, would be enough world wide. I do not believe the NA versions (Tacoma/4Runner) are significantly less durable than versions (Hilux/Fortuner), or that it would cost too much to make the Hilux/Fortuner NA viable. Toyota's BOF lineup is from a time the market was not SUV/CUV crazy, now it also has to adapt. The main issue seems to come for the development and life-cycle. the BOF car Sequoia and Land Cruiser are really very old. But Toyota is not as small as Mitsubishi with their old, yet very well built and still competitive Pajero.
The Lexus LF-1 is the first step in the right direction (for Lexus), not only for NA, but specially for Europe and Asia. Regarding Toyota's last CUV/SUV concepts, 3 of them, they better be functional. Unfortunately the functionality gets lost from concept to production.
One thing that is sure, is that Toyota will remain a BOF vehicle manufacturer, because until there is a breakthrough in sustainable energy, that is abundant, can be easily transported and accessed from the most remote places, until autonomous cars can drive in the most remote and unpredictable places, BOF vehicles are here to stay, few compared to the whole consumer market, but quite enough to make a profit, and TMC better be a leader in this domain. 'Green' will no more be a selling point, when every car will be 'green'.