I experimented recently with increasing a texture size over and over while painting single stripes to create the sense of rising land. This left artifacts where the pattern repeated in unpleasing ways, but largely this worked. I also stamped a few small trees at the “bottom” and larger at the “top.” I think a way to assign texture size to a separate texture map would work. A simple gradient of white to black across the map could be a gradual shift of texture size of 20 to 150, simulating a hill. A number of artists achieve multiple levels cleverly, but hills seem especially hard.
