Among various stakeholder-based multi-criteria group decision-making (MCGDM) frameworks, Multi-Actor Multi-Criteria Analysis (MAMCA) stands out for its emphasis on exploring preferences and conflicts among stakeholder groups. MAMCA ensures comprehensive stakeholder assessments, integrating diverse perspectives into the decision-making process. However, existing MAMCA software faces limitations in accommodating large participant bases, a challenge amplified by the increasing demand for online stakeholder workshops. This study extends the MAMCA software by incorporating survey-based evaluation methods, evolving it into a survey-based decision-support system (DSS). This enhanced DSS facilitates output-level aggregation within stakeholder groups, enabling detailed collection and aggregation of individual preferences. The survey-based DSS includes new developed survey-based techniques such as the Simos method and Simple Multi Attribute Rating Technique (SMART), which streamline the weight elicitation and alternative appraisal processes. These methods ensure an intuitive and accessible evaluation process, suitable for both online and offline workshops. A case study evaluating Swiss energy policies demonstrates the effectiveness of the survey-based DSS, highlighting its ability to support comprehensive stakeholder assessments and facilitate understanding across diverse groups. This approach improves stakeholder engagement and promotes transparency throughout the decision-making process, ensuring inclusive decision outcomes.