Meanwhile we are waiting for a propa mod, I modified an existing Autohotkey script slightly, so it will only work within the Fallout4 instance/windows (and not in your browser etc). to toggle your aim with clicking your right mouse.
Just copy this into an empty .txt file and load it with Autohotkey:
SetTitleMatchMode, 2
#SingleInstance Force
#IfWinActive, Fallout4
*RButton Up::
If (Toggle := !Toggle){
Send {Click Down Right}
}
Else{
Send {RButton up}
}
Return
#IfWinActive