What is the ruling on the Imam saying aloud: “O Allah, bless our master Muhammad, my support and my beloved,” after the Iqamah and before the Takbirat al-Ihram?

Praying upon the Prophet, peace and blessings be upon him, after the Iqamah is considered mustahabb (recommended) by some scholars, by analogy with the Adhan, based on the Prophet's saying: «When you hear the Mu'adhdhin, say as he says, then send blessings upon me, for whoever sends blessings upon me once, Allah will send blessings upon him ten times.» However, describing the Prophet, peace and blessings be upon him, as a "sanad" (support/crutch) is an unacceptable exaggeration (ghuluww); for the believer relies solely on Allah. The best form of prayer upon him is the Salat al-Ibrahimiyyah.