Mass Individualisation is a new product design paradigm that comprises an open-hardware platform and multiple independent modules for end-user’s selection that are integrated with the platform. Open platform architecture products (OPAP) are the key enablers for this paradigm. Based on explorative literature analysis, with practical insights from an industrial questionnaire survey, an Innovation toolkit for the end-user has been developed. This provides a means for selecting an optimal OPAP. The design of the Innovation toolkit has been approached in four different steps: modelling of OPAP Products; modelling of evaluation measures and evaluation indices with end-user preferences; identification of the optimal module options for every configuration and Configuration optimisation. Two case studies have been presented to demonstrate the effectiveness and to illustrate that the Innovation toolkit can readily be applied to these types of product development to obtain highly individualised and optimised OPAP.