Electronic signatures are an established method to ensure the integrity and accountability of electronic transactions. Realizing their potential, the European Parliament and the Council enacted the directive 1999/93/EC in 1999, providing legal requirements for a common introduction of electronic signatures in Europe. However, so far the signature market has failed miserably. Mobile electronic signatures are often seen as a potential and promising way to provide market acceptance for electronic signatures. This paper proposes an infrastructure for qualified mobile electronic signatures that does not require the mobile operator to act as a certificate service provider (CSP). The user can freely choose a CSP and add the signature functionality along with the required certificates later on demand. However, mobile operators will only invest in this infrastructure, if they expect a return on investment (ROI). Therefore, based on our proposed infrastructure and using distinct scenarios, we conducted an investment analysis for mobile operators forecasting the net present value and the internal rate of return of the investment. Our forecast shows that issuing signature capable smart cards can be quite profitable for a mobile operator.