  Cosmic rays (CRs) are an integral component of the interstellar medium,
producing broadband emission while interacting with other Galactic matter
components like the interstellar gas or magnetic fields. In addition to
observations, numerical simulations of CR propagation through the Galaxy help
to increase the level of understanding of Galactic CR transport and diffuse
$\gamma$-ray emission as seen by different experiments. Up to now, the standard
approach at modelling source distributions used as input for such transport
simulations often rely on radial symmetry and analytical functions rather than
individual, observation-based sources. We aim at a redefinition of existing CR
source distributions by combining sources observed with the H.E.S.S. experiment
and simulated random sources, which follow the matter density in the Milky Way.
As a result, H.E.S.S.-inspired Galactic CR source distributions are inferred.
We use the PICARD code to perform 3D-simulations of nuclei and electrons in CR
propagation using our hybrid source distribution models. Furthermore, also
gamma-ray maps and spectra, simulated with the redefined source models, are
evaluated in different regions in the Galaxy and compared with each other to
determine the statistical scatter of the underlying distributions. We find
global consistency between our models and in comparison to previous
simulations, with only some localised fluctuations, e.g. in the spiral arms.
This implementation of a three-dimensional source model based on observations
and simulations enables a new quality of propagation modelling. It offers
possibilities for more realistic CR transport scenarios beyond radial symmetry
and delivers meaningful results in both the arm and interarm regions of the
Galaxy. This gives a more realistic picture of the Galactic $\gamma$-ray sky by
including structures from the source model and not just the gas distributions.
