CubeSats are a type of spacecraft which have become popular since the early 2000. They are known for their quick development time and low cost, when comparing them to larger satellites. However, there is a significant drawback which has been recorded during these years of operations, namely an high failure rate which turns almost half of them into space debris. The reasons behind these malfunctions are often attributed to flawed spacecraft design choices or failures of commercial off-the-shelf (COTS) products. To improve the design of CubeSats, several software tools for performing the conceptual design have been proposed. These tools are often limited in their capabilities and are not suitable for all types of CubeSat missions. To address this issue, the University of Applied Sciences Wiener Neustadt (FHWN) in cooperation with Technische Universität Dresden is developing a software tool called GREATCUBE+. Its goal is to increase the success rate of CubeSats by providing a satellite model which is composed of commercial-off-the-shelf (COTS) products backed up by empirical heritage, analytical proof, and numerical analysis. One of the main features of this tool is the ability of dealing with different typologies of payloads. GREATCUBE+ has been validated with various successful CubeSat missions and it provides design solutions with an accuracy of above 90% when it comes to CubeSat weights and volumes. Using this software, CubeSat design teams can proceed from the conceptual development to the testing and assembly phases quicker, hoping to result in higher quality CubeSats and fewer failures.