The losses caused by the 2023 Kahramanmaras earthquakes once more showed that determining the seismically deficient buildings and risk mitigation of sub-standard building stock in Turkiye is quite an urgent challenge. Considering the required time and cost of conducting seismic safety assessment of large building stocks, code-based detailed assessment approaches cannot respond to the urgency of widespread implementation of structural evaluation efforts; less time-consuming and yet highly accurate procedures need to be implemented. Towards the risk mitigation studies in Istanbul, more than 25,000 sub-standard reinforced concrete (RC) buildings were inspected using the structural mechanics-based PERA2019 rapid evaluation methodology as the first step. The outputs of this pilot study revealed that the evaluated building stock is far from satisfying the seismic demand defined in the 2018 Turkish Building Earthquake Code for existing buildings. To prepare the mega-city, Istanbul, for a future earthquake and minimize the seismic-induced losses, structural retrofitting interventions must be implemented widely. In this study, seismic risk distribution in Istanbul is outlined. Based on the analysis results of the evaluated buildings, the need for structural rehabilitation studies is discussed. Finally, the potential role of FRP composites in risk mitigation efforts in Istanbul is assessed based on parametric studies conducted on a group of sub-standard RC buildings, and a cost/benefit analysis for the effectiveness of FRP composites on loss and risk reduction is presented considering different scenarios.