Personally, I would never allow such a scaling option to be used - period. To me, that is just asking for trouble and opening a door that should not be opened.
Also, the "limitation" you are talking about is not a limitation of the spell, but of how magic works (i.e. there is and never will be an official spell where a character can tell another character to kill themselves and they will). So, IMO, no amount of scaling will or should ever overcome that.