I reckon that life bars will definetly change Feral Heart completely whether that is in a good or bad way, it will definetly make a difference.
In my opinion (I know it would be complicated) but perhaps a system where you can choose to fight by selecting like a "Threat Mode"? Which would engage your char in attack status. Or perhaps there could be certain maps where only attacks or fights may be enabled in-game, such as a 'PVP' (Person Versus Person) map.
However, I do believe that it may give 'trols' of Feral Heart an advantage to gang up on people and victimize them at that, this would be unacceptable and complaints might be made from parents as it may display aggression/violence AND bullying. (This does not mean I do not trust the moderators, but they have lives of their own to attend to and may not always be there to 'save the day', this I do respect.)