The continuous effort to increase railway capacity is supported by modern technologies such as the European Train Control System (ETCS). ETCS Level 2 without signals (ETCS-L2oS) is the preferred level for rollout in Germany. To ensure the capacity gains from these systems, optimizing block division (the distance between ETCS signals) is crucial. The challenge lies in deriving a capacity optimal block division while adhering to established planning rules. These rules, although restrictive, are not absolute and may change over time. Currently, few approaches exist for optimizing block division in ETCS L2oS. Most aim to adjust block sizes for specific train sequences without considering the placement restrictions of ETCS signals, failing to meet practical requirements and future capacity needs. This article addresses these gaps by proposing a novel heuristic approach to optimize block division on ETCS L2oS lines. By incorporating flexible restrictions and flexible computation, the approach ensures that block division is optimized for both current and potential future requirements.