Partial charges outside of the atoms center

If I understand you correctly, what you are trying to do is to calculate the potential on a grid as a result of the (in the example) HF molecule and then find the partial charges at different points away from the atom centers, that still mimics the potential on that grid (which is the purpose of the ESP fitting code).

I can see what youw ant to do used in for example replacing multiple atoms, each with partial charges, with one to do coarse-graining in MD.