Is the LC 250 truly customizable: Can you change media screen (8" for 12.3") and can you swap headlights (square/round)?

[APIOQM]

It makes one wonder why a 12.3" screen wasn't part of all Land Cruisers (and Prados) to begin with, instead of an 8" in just one trim level (i.e., 1958).

It seems like such uniformity would've been much simpler and a lot less expensive for Toyota.

Because Toyota wants to incentivize people to spend more money on the higher grades. What they would save in production cost they would lose in more sales going to the 1958.