The ideology promoted about building NewSpace small satellites includes short development times and “off-the-shelf” parts for cost effectiveness. Already based on these criteria, a 120kg satellite named “Flying Laptop” was developed at the Stuttgart University in cooperation and guidance from Airbus. It was launched in 2017 and is still reliably operational, has three axis stabilization and uses off-the-shelf units. The development while fulfilling some main criteria also showed deficiencies. Until launch it took more than 7 years and scalability was achieved only for the software. Airbus from this baseline initiated a consortium with diverse SMEs in a continuous effort to optimize the ideology and technology about building satellites. Tenets of this “{\it F-Series}” approach include automotive-like Scrum development and continuous verification, scalable avionics, again employing “off-the-shelf” parts, a consistent path from early digital twin to full flight hardware/software/operations featuring flexible payload connectivity. Considering the main takeaways from diverse modelled satellites and studies, the {\it F-Series development kit} for building SmallSats emerged. Its key elements are \begin{itemize} \item hardware - the modular onboard computer and power units, sensors, actuators/propulsion, \item flight software – highly configurable w.r.t. satellite modes, orbits, single/multiple payload control, \item the digital twin (satellite simulator), \item intelligent payload subsystem and \item an operations suite featuring full encryption. \end{itemize} This paper will discuss each of these elements in detail. In order to refine the development time, the kit comes with an agile plan helping users eliminate any uncontrolled processes and reworks. It is based on {\it development benches} also being part of the kit. These benches – digital twins – are starting from a fully simulated satellite including the flight software source and provides connectivity to various mission control suites. After the SmallSat design having reached a certain development readiness, the hardware core avionics are available for seamless connection to the existing simulator replacing formerly simulated units. The process evolves up to the final satellite flight model. The {\it development kit} is usable both for CubeSats and SmallSats. By applying the same software and similar avionics and operations concept, the scaling of satellites becomes straightforward, permitting to keep all the supporting infrastructure and trained personnel. This paper cites CubeSat example missions like “EIVE” and the Swedish/German AI mission “ICE-Brain-1” and explains how such a development kit overcomes scalability challenges, and operational flexibility limits. Finally, the paper lists different SME partners of the {\it F-Series consortium} with shared ideologies.