I have already spoken on many occasions about the problem of the Russian BMP's

I have already spoken on many occasions about the problem of the Russian BMP's cabin and its insufficient space and protection (although this can be solved with extra armour).
The space problem is structural and can only be solved by re-building the vehicle.
In this case, the field engineers decided to completely forgo the passenger compartment, which is never used for troop transport anyway, and welded in a staircase where the door would be.
This leads to a new troop compartment created above the factory one.