Wa `alaykum as-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
In all acts or worship (`ibadat) we are to strictly follow the Shari`ah rules. This kind of Prayer you have described has no basis in the Shari`ah. So, it is not allowed to perform it.
In his response to your question, Sheikh Ahmad Kutty, a senior lecturer and an Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states:
There is no precedent for this in the practice of the Prophet (peace and blessings be upon him), the Companions or the pious predecessors. We must not introduce such practices; it amounts to interfering with the established form of Prayer as passed on by the Prophet (peace and blessings be upon him).
If it had been a good practice to stand up and send salutations of peace to the Prophet (peace and blessings be upon him) in this way, the pious predecessors would have done it.
Allah Almighty knows best.