Lock Target on Allies(heroes)

Hows about heroes being able to target lock allies, that will do the following:
In Agressive mode: Force them to attack anything within the attack range of the locked ally.
In Defensive mode: Force them to attack anything attacking the locked ally.
In Passive mode: Stand by and do nothing except:

The following must be in effect no matter the mode:
The hero must cast and maintain enchantments on the locked ally, and the hero must prioritize healing and resurection to that ally.

So basicaly, if you have a Protection Monk Hero, and you target lock some person you have to defend, or another party member, that hero will go to that person/ally and cast protection spells on him/her.