As environmental policies tighten and consumers demand sustainable products, transitioning from a linear to a circular economy is crucial. A promising approach to circular economy is remanufacturing end-of-life electric machines to meet original or new specifications. Designing a rotor for remanufacturing with a different topology to fulfil the new requirements is a complex, non-linear optimisation task. In this paper, a permanent magnet-based synchronous machine is transformed into a synchronous reluctance machine with a new rotor topology. In this research, the Taguchi method is used to estimate parameter sensitivity. For optimisation, the Non-dominated Sorting Genetic Algorithm II was selected. Multi-criteria decision-making methods also helped choosing the optimal designs for maximum torque and minimal torque ripple. The sensitivity analysis revealed that the cut-off barrier shape significantly affects the average torque. In contrast, the height of the inner flux barrier had the most negligible effect. Most parameters showed almost the same magnitudes to torque ripple except for the height of the flux barrier, which again was the least significant. TOPSIS and SPOTIS methods using statisticalvariance and entropy weights showed some disagreements, indicating the complexity of selecting the optimal design.