I'd separate your foreground asset approach from your background asset approach — height blending will work fine where the player can't get up close and personal with it, and decals/floaters will get the job done for the front-and-center stuff. You could also try some fancy stuff with POM floaters, if you're looking to…
For me vertex paint would be good, but not alone. To get correct edges between textures you can use mask texture to get irregular transition between textures. This will give you an ability to control how those textures are mixed. Also to break up texture repetitiveness ( brick in this case ) you can use floater geometry.…
thank you very much guys. so far i tested hight blend and by pushing the plaster it works quite fine for the first approach but i think i will also work with pom floaters and decals. Maybe i also try sth with cutting parts out and using different ids together with decals to get good edges