The TERRAIN lump/file already has the ability to define a sound from SNDINFO when the player drops on a specific flat (e.g a heavy wood creaking sound when you land on a wooden flat), but as the wiki article mentions that is different from a footstep sound that plays when you simply walk across a particular flat.
So I was wondering if it would be possible to add a property in TERRAIN that allows you to define a sound that plays when you walk across a flat, which I'm guessing would also make the sound play faster the quicker you move across the flat, perhaps with the speed at which the sound plays being a configurable property too. The later would be useful if for example you walked over a flat and the footstep sound played too fast for some reason, so you could just set the footstep speed property for that TERRAIN definition down to 0.5 to half the speed at which the footstep sound plays. Would also be nice if it could be implemented to have monsters also make footstep and/or drop sounds as well.
Note: In case anyone suggests that I use The Zombie Killer's ACS footsteps mod, or its' ZScript port. I know about them but they are fairly difficult to set up and use, and they exist to implement something that should already exist natively anyways. Through a simple property or two for mappers to use, not by having to import an ACS or ZScript library to your map, mapset or mod just for being able to hear the sound of dirt when walking across a dirt floor.