  We discuss recent progress in the development of the three-fluid
hydrodynamics-based program THESEUS towards an event generator suitable for
applications to heavy-ion collisions at the intermediate energies of the
planned NICA and FAIR experiments. We follow the strategy that modifications of
particle distributions at the freeze-out surface in the QCD phase diagram may
be mapped directly to the observable ones within a sudden freeze-out scheme. We
report first results of these investigations for the production of light
clusters (deuterons and tritons) which can be compared to experimental data
from the HADES and the NA49 experiment and for the interpretation of the "horn"
effect observed in the collision energy dependence of the $K^+/\pi^+$ ratio.
Medium effects on light cluster production in the QCD phase diagram are
negligible at the highest NICA energies but shall play a dominant role at the
lowest energies. A sharp "horn"-type signal in the $K^+/\pi^+$ ratio can be
obtained when the onset of Bose condensation modelled by a pion chemical
potential results in an enhancement of pions at low momenta (which is seen at
LHC energies) and would occur already in the NICA energy range.
