A droplet deformation model based on the combination of an axisymmetric Boundary Element Method (BEM), Viscous Potential Flow (VPF) theory, and a simplified heuristic model for the action of aerodynamic forces is presented. The model predicts droplet distortion and interface shape up to the point of initial droplet break-up. To address liquid viscosity a previously introduced Generalized Viscous Pressure Correction was employed after its extension to 3D axisymmetric cases. Assumed are thin boundary layers within the droplet phase, a high density ratio between the two phases and moderate Reynolds numbers. The model requires at most around 200 flow variables to properly predict droplet deformation and distortion. The overall model produces results comparable to those of the Taylor Analogy Breakup model and its nonlinear version in the vibrational regime. However, it requires a calibration factor of 1.36 for the aerodynamic local pressure, in order to obtain the correct critical Weber number of around 12. In the bag and bag-stamen regimes, the droplet shape and distortion parameters are in good agreement with experimental data. Overall, the results indicate that the present modeling approach might be used as sub-grid model for droplet dynamics in multiphase flow simulation with a highly dispersed liquid phase.