The wetting behavior of a liquid polymer on top of a supported glassy polymer film is investigated with real (optical microscopy, phase measuring interference microscopy, and scanning force microscopy) and reciprocal space analysis techniques (X-ray reflectivity and grazing incidence small-angle X-ray scattering). The thermodynamic stability of the top film is determined by the interface potential that results from an interplay between short-range and long-range van der Waals contributions. It comprises two competing minima which correspond to a film of vanishingly small, microscopic thickness and to a film with a larger, mesoscopical thickness of a few nanometers. At high temperatures, the liquid top-layer forms drops sitting on top of this mesoscopically thin film. The short-range contribution influences the equilibrium state, and the long-range part of the interface potential determines the kinetics of dewetting. By varying the thickness of the glassy, polymeric sublayer, the effective interface potential is tuned, and a dewetting of the top layer is observed. Additionally, we find the kinetics of hole growth to be compatible with a reduction of the PA sublayer viscosity compared to the bulk.