Autonomous mobile robots with manipulators are becoming increasingly important in industry because they are the most flexible type of mobile robots. Therefore, these mobile robots are employed in dynamic, heterogeneous and partly structured environments. However, as depicted in ANSI/RIA R15.08-1-2020, new safety requirements focusing the fitness of the mobile robots to its operational scenarios arise. In contrast to fenced industrial robots, mobile robots need to reason about their environment, specifically the monitored space and adapt accordingly. However, since the monitored space is often limited, today’s autonomous industrial mobile robots type C (IMR-C) as R15.08-1-2020 names this kind of robots waste much potential reducing their pace of work due to limited monitored space. To counteract this issue, we first analyze the effects of limited monitored space using system theoretic process analysis (STPA) and then come up with a novel monitoring tool closing the blind spots of the IMR-Cs. The comparison of the STPAs with and without external monitoring tools show risk reduction in the original loss scenarios but new loss scenarios and consuming effort in order to assemble them. We present a methodology to weight the gains and losses of assembling an additional monitoring tool using the Digital Twin. The evaluation of our prototype in a goods receipt scenario shows promising results.