@JeffMOD
Pseudo-3D? I'm not sure what that is, but I guess it's the 2.5D feature of DOOM, because it was essentially 2.5D, but rendered as 3D.
There will be hidden areas if I make them fit into the map (and probably I will, such as a mini-cinema).
No filtering? Maybe if you turn on Software mode.
Sector-based lighting? Heh, GoldSource doesn't probably support that natively, however I could convert each "sector" to a func_wall, and then control their minimum light level. But no.
What I really meant by the mentioned method, was actually this: "every floor; different wall texture".
It implies that for every new floor/sector, there has to be a different wall or floor texture for each floor.