Service-oriented Software Engineering (SOSE) is a software engineering paradigm focused on Service-oriented Computing Applications (SOCAs), for what SOCA development methodologies are required. Recent studies on SOCA development methodologies revealed theoretical and practical deficiencies. Thus, academicians and practitioners must adapt development methodologies from other paradigms or use the available partial SOCA development methodologies. Also, since the high acceptance of agile approaches, we claim new well-structured and balanced agility-rigor methodologies are required. Then, this paper proposes a new SOCA Development Systems Engineering Methodology, including its description, the explanation of its theoretical foundations and the illustration of its use with a prototype of a running example. Two pilot empirical evaluations on usability metrics are also reported. Findings support both theoretical adequacy and positive perceptions from the evaluators. While further empirical tests are required for gaining more conclusive evidences our preliminary results are encouraging.