Blender already does something like that with the cast modifier.
Could what I am suggesting be some sort of derivation of that, whereby you add a tool to the sculpted mesh (something as simple as a plane would work - perhaps with a variable offset). This plane would repel any vertices that got too close, a bit like what the cast modifier does when you move your object closer to the cast control object.
It would act as a barrier/constraint. If you inserted this tool between two parts of the mesh you didn’t want to intersect (like fingertips) you could then sculpt the vertices either side and they would maintain their separation.
This screenshot might illustrate it better. I have two spheres both with the cast modifier applied. The empty is the control object (set to cuboid). As I move the spheres closer together, their vertices flatten as they hit the cuboid’s area of influence and looks for all the world like the two spheres are repelling each other. Now imagine instead of a cuboid, the cast control object was thin plane. You could move the spheres closer together and their vertices would be squished up against the plane thus maintaining separation. If the plane was thin enough, it would look like the spheres were actually pressed up against one another.
In the real world it would be like placing a thin piece of glass between two parts of a clay model, sculpting up to the glass, then removing it.