Calling it now; this nice smiling guy is a special agent for the principal who does all the dirty backroom shit. This entire invitation and mock battle is a trap to make Usato show his skills so they can implement countermeasures.
I think Halfa's job is to make everyone aware of what good healing magic is capable of.
Having a powerful tool shunned by scholars is a bad thing so he try to make them understand it's importance.