Molecular photoswitches including HTI are highly sensitive to the environment and it is of critical importance to understand the details of solvent effects or HTI embedding in molecular assemblies such as self-assembled monolayers. We therefore advocate for explicit solvent models and extended statistical sampling -which implies 10,000s of atoms sized simulation systems and 100 ns scale dynamics runs, respectively. This calls for computationally efficient approaches that largely replace quantum mechanical (QM) calculations by molecular mechanics (MM). This may be accomplished by multistate force-fields to specifically describe Born-Oppenheimer potential energy profiles at a given electronic state. The latter are routinely available for the ground state, however for photoswitches we also need specific force-fields for describing the modification of the atomic forces upon electronic excitation. As a minimum requirement, at least the most relevant excited state, typically the adiabatic S1, needs to be mimicked by a tailor-made MM interaction potential.