thanks for the kind comments
there’s plenty of room for improvement, but sadly I’ve hit some limitations already.
the first thing is that I realized that to have different Physical Materials in a landscape (so there can be different footstep sounds/particles where you step) the only way to do it is to have a different PhysMat per layer. with the current material setup this would result in the same sound/particle for snow, rock and grass.
I think I’ll post a request on the answerHub but I don’t have high hopes for it 
edit: made the AnswerHub question about physical materials]
the second thing is that from what I saw, I pretty much hit the limit of the things I can play with it to make procedural stuff in the material. namely I only have the slope values and nothing else to use.
I wanted to attempt the creation of something similar to the flow maps I’ve seen from some WM terrains, and for what I would need the heightmap or at least the geometry normalmap in a texture so that I can offset it and compare it with the non-offset one. I made an AnswerHub question about the Heightmap in the material] but went to second page in less than 2 hours. again I don’t have high hopes for it (answerhub is too crowded and it seems epic has their own kinda-rigid agenda of features)
and beside that I’m out of ideas on how to do stuff procedurally other than using slopes and pure height values.
at this point the only thing I think I could do would be to generate and update layer splatmaps from code at editing time dynamically, but I would need to grab the editor source and either try to make a plugin or modify the behavior directly. all of this is not nice and would take weeks to do and I’m not even confident I would be able to.
so I’m open for suggestions 
also I haven’t decided on the public exposure on this yet. maybe I’ll sell it on the marketplace for $1 
don’t expect many updates btw. like I said I barely have time to work on this (too focused on finishing my main project), but whenever I do something new I’ll post updates