Question regarding Vanilla Doom falls

Since Doom 2 supports actual "water"fall textures, would it be possible to recreate that for Doom 1 using the normal liquid flats as wall textures in vanilla Doom? I know it works in ZDoom, but I'm not sure if it can b done in a non-source port environment.

IIRC all the animated texture and flat sequences are availible to both Doom1 and 2.

Vanilla Doom did not support texture/flat mixing; that is something that sourceports such as ZDoom and Doomsday etc etc, have added.

You could load the fwater flats into your wad as textures and rename them so they replace one of the 4 frame animated textures.

You can load any texture into a WAD (level) you are creating (as long as the format is correct) and still have it be vanilla compatible. I recommend using Slade3 as your editor:

http://slade.mancubus.net/

And Doom 1 textures from realm667's repository:

http://realm667.com/

You will need to become familiar with Slade3 as well as the Doom engine to do this correctly, but this is a good place to start. Once you know what you are doing you can load a wide range of textures and flats (floor and ceiling textures) into your levels with ease and have them still be vanilla compatible.