By Valentina Za and Giuseppe Fonte MILAN (Reuters) – Monte dei Paschi di Siena’s (MPS) plan to proceed with a capital raise is entering a decisive stage with CEO Luigi Lovaglio and the banks due to guarantee the sale still hammering out final details, people close to the matter said. MPS aims to launch the new share issue for up to 2.5 billion euro ($2.5 billion) on Oct. 17. That would allow it to raise funds in time to lay off staff under early retirement rules expiring at the end of November – barring new legislation to extend them. To meet its deadline MPS must approve the terms of the shar…